AIR CONDITIONING

CONTENTS OF THIS SECTION

Since the combinations of temperature, relative humidity and air movement which satisfy personal comfort fall within considerably narrower limits than nature usually supplies, a means of controlling these factors is essential if maximum conditions of comfort are to be attained. In addition to the discomfort resulting from too little or too much heat, the atmosphere often seems heavy and unpleasant from the excessive humidity present. Since the moisture content of the air may be close to saturation, body moisture is not absorbed at a satisfactory rate.

body comfort in today's passenger cars has directed attention toward the development of an automotive air conditioning system that will be capable of producing desired comfort for the occupants under all climatic conditions.

Operating on the same basic principles as the modern home air conditioner, the 1957 Chevrolet all-weather air conditioning system is designed to provide the controlled temperature and humidity requirements for year around riding comfort. Components of the system are all located compactly under the instrument panel and hood of the car (figures 1 and figure 5).

The system operates either on outside air or on recirculated inside air. Outside air is introduced into the system through the right fender air duct (fig. 3) and immediately passed through the evaporator unit. A three-speed blower directs the air to a distributor mounted on the dash panel inside the vehicle (fig. 2). Conditioned air then entersthe passenger compartment through the two instrument panel adjustable outlet nozzles and either the floor distributor or defroster manifold in proportions determined by control settings. Air is recirculated back through the unit from the car interior by means of the right hand ventilator when the air central lever is at the INSIDE position.

The desired heating capacity is obtained by metering the flow of engine coolant through the heater core. The de-humidifying feature is achieved by passing incoming air through the cooling coils where excess moisture condenses and is drained from the system. Dirt and dust in the incoming air adheres to the damp surface of the cooling coils and is discharged through the drain along with the condensate. The temperature of incoming air is then raised to the desired level as the air passes through the heater core.

By a simple manipulation of controls, the right combination of temperature and humidity may be easily obtained regardless of weather conditions. In addition, inside air may be recirculated through the system where contaminated air is encountered, such as in concentrations of slow moving traffic.

Controls

Since the factors which determine the condition of outside air vary independently, they require independent controls. Six controls (fig. 1) adapt the system to a wide range of such variations.

The six control levers move through slots in the control panel mounted in the instrument panel to the right of the driver.

• COOLING-Two levers comprise the cooling controls for the air conditioning system.
• The COLD lever regulates the temperature of the air as it leaves the evaporator. As this lever is pushed down approximately one quarter of an inch the thermostatic control switch, part of the cool air temperature control unit, is closed. As the lever is pushed further down the temperature setting of this adjustable thermostat is lowered.
• The OUTLET lever allows a choice of outlets to be used for diffusion of the cold air into the car. With this lever all the way down, air flow will be directed to the dash diffuser nozzles. As the lever is pushed up the air flow is gradually diverted to the floor distributor assembly. With this lever all the way up the entire flow of air will go to the floor distributor assembly.
• HEAT-This lever adjusts the hot water thermostatic valve. Moving the lever down increases the temperature setting. The heat output required to maintain the desire of temperature within the car is obtained by continuous thermostatic regulation of the flow rate of hot water through the core.
• DEFR-This knob, as it is moved down, positions the defroster door. As the knob is moved down, the amount of air directed to the defroster ducts is increased.
• AIR-This lever controls the damper in the right fender air duct and may be set at either INSIDE or OUTSIDE to determine the source of air supply. When positioned at OUTSIDE air the conditioning unit receives outside air directly through the right fender air duct. When outside air becomes excessively contaminated, the lever may be moved to INSIDE air. The blower will then recirculate inside air through the conditioning unit. Under extreme high humidity conditions it may be desirable to operate, as much as possible, with this lever set for INSIDE air. Should unheated and uncooled air be desired, this lever may be set at the intermediate position allowing outside air to flow directly into the vehicle without going through the heating or cooling cores.
• The VENT lever to the extreme left of the control panel controls the damper on the left fender air duct allowing outside air to enter the vehicle.
• At the top of the Air Conditioning control panel is the three speed blower switch.
• Below the Air Conditioning Control Panel is the Fast Idle Knob. Pulling this knob out will provide a slightly higher engine idle speed to give satisfactory cooling when parked or stopped. CAUTION: Car selector lever should be in Park or Neutral position before pulling this knob out.

• Refrigeration is the process of removing heat.
• Heat is a form of energy.
• There is actually no such thing as "cold". Cold may be defined simply as the lack of heat.
• All matter exists in either a solid, a liquid, or a gaseous (vapor) state. The physical form or state of any substance depends entirely upon the amount of heat that it contains. Many substances familiar to us can be readily converted from one physical state to another by the addition or removal of heat. Example: Water to steam or water to ice.
• Heat always travels from the warmer object to the cooler object.
• Adding heat to a substance causes it to expand.
• Heat can be measured in two ways-Intensity and Quantity. The intensity is measured with a thermometer in units called degrees. The standard of measurement for quantity is known as the British Thermal Unit, commonly called the BTU, which is defined as the amount of heat required to raise the temperature of 1 pound of water l Fahrenheit. The difference between intensity and quantity may be illustrated with two containers filled with I and 2 pounds of water respectively, each at the same temperature or intensity. We know however, that there are twice as many heat units in the 2 pound container as in the 1 pound container, since it will take twice as long to raise the temperature of 2 pounds of water the same number of degrees as 1 pound of water.
• Two kinds of heat are sensible and latent. Sensible heat is heat that changes the temperature of a substance with no change in the form of the substance. Latent heat is the heat that changes the form of a substance without changing its temperature. For example, if water is heated anywhere below the boiling point, sensible heat absorbed will cause the temperature to rise until the boiling point at 212°F. is reached. However, at the boiling point, additional latent heat will be absorbed to convert the water to a vapor but the temperature will remain at 212°F during boiling. For water, 1 BTU is the amount of heat required to raise the temperature of 1 pound of water 1°F or 180 BTU's are required to raise the temperature of 1 pound of water from 32°F to 212°F. If the 1 pound of water was then boiled until all the liquid was converted to vapor at 212°F, 970 additional BTU's would be absorbed to accomplish the conversion. Thus when a liquid boils, turning to vapor, it absorbs a great amount of latent (hidden) heat without changing temperature. This heat is known as Latent Heat of Vaporization. Conversely, when the vapor is condensed, the process is reversed and the same amount of heat is released in converting the vapor to liquid. This principle of large heat absorption or release that occurs when a liquid changes to vapor or a vapor condenses forms the basis of modern refrigeration systems.
• Vaporization is the conversion of a liquid to a gaseous or vapor state at the boiling point of the liquid. Evaporation is the conversion of a liquid to a vapor state at a temperature lower than the boiling point of the liquid.
• Although the terms evaporation and vaporization are closely associated, there is a distinct difference between them. If we place a glass of water in a room, we know that eventually the water will evaporate. This is due primarily to the fact that the air above the water is in constant motion and contains a comparatively small amount of moisture. Nature attempts to produce an equilibrium between water in the glass and water in the air. Because of the large volume of drier air and small volume of water, all the molecules of water will eventually change to vapor and be carried away by the air. If we place a sealed cover over a glass of water in the room, the water will evaporate only until the air above it holds all the moisture that it can contain at that temperature. If the process of evaporation is sufficiently rapid, a noticeable reduction of temperature can be felt. This is known as evaporative cooling.
• The term "hot" is not necessarily associated with a boiling liquid. Freon-12, the refrigerant used in Chevrolet's air conditioning system, boils at 21.7°F below zero. Thus, if it were exposed to the air at normal room temperature, it would absorb heat from surrounding areas or objects and boil, immediately changing to a vapor.
• Saturated Vapor is vapor which is in contact with its liquid and which is at the same temperature as the boiling point of its liquid. It will remain saturated as long as it is in contact with its liquid. All vapors used in a refrigeration system are saturated vapors.
• Superheated Vapor is vapor which has its temperature increased above the boiling point of the liquid from which it came.
• Compressing a vapor increases its temperature and conversely, expanding a vapor decreases its temperature. A tire hand pump, for example, will become warm when pumping air into a tire due to the heating of the air as it is compressed.
• Any vapor can be liquefied by squeezing or compressing it if sufficient pressure is exerted.
• All pressure, regardless of how it is produced, is measured in pounds per square inch (psi).
• Atmospheric Pressure is pressure exerted in every direction by the weight of the atmosphere. At higher altitudes air is rarified and has less weight. At sea level atmospheric pressure is 14.7 psi.
• Any pressure less than atmospheric is known as a partial vacuum or commonly called a vacuum. A perfect vacuum or region of no pressure has never been mechanically produced.
• Gage pressure is used in refrigeration work. Gages are calibrated in pounds (psi) of pressure and inches of vacuum. At sea level 410)1 lbs. gage pressure is equivalent to 14.7 lbs. atmospheric pressure. Pressure greater than atmospheric is measured in pounds (psi) and pressure below atmospheric is measured in inches of vacuum. The "O" on the gage will always correspond to the surrounding atmospheric pressure, regardless of the elevation where the gage is being used.
• All liquids have a definite boiling point, which is dependent upon the pressure applied. Water for example will boil at 212°F only at sea level atmospheric pressure. If the pressure is increased the liquid will not boil until a higher temperature is reached. Thus Freon-12, which would normally boil at 21.7°F below zero if exposed to the atmosphere, can be prevented from boiling if it is kept under high pressure. Conversely, if the pressure is decreased, the liquid will boil at a lower temperature.
• When the pressure of a vapor is increased, the temperature at which it will condense is also raised.
• A definite pressure and temperature relationship exists in the case of liquid refrigerants and their saturated vapors. Increasing the temperature of a substance causes it to expand. When the substance is confined in a closed container, the increase in temperature will be accompanied by an increase in pressure, even though no mechanical device was used. For every temperature, there will be a corresponding pressure within the container of refrigerant. A table of the temperature-pressure relationship of Freon-12, which is used in the Chevrolet system, is presented below. Pressures are indicated in gage pressure, either positive pressure (above atmospheric) in pounds or negative pressure (below atmospheric) in inches of vacuum.
• Any refrigeration system takes advantage of the principles described above. The simplified refrigeration system illustrated in Figure 4 contains five basic parts; a compressor, a condenser, a receiver, an expansion valve and an evaporator. Assuming Freon-12 as our refrigerant, let us follow through the refrigeration cycle:

Freon gas under low pressure is drawn into the compressor where it is compressed to a high pressure. During compression, the Freon gas is heated. When sufficient pressure is built up, the hot Freon gas passes into the condenser where it cools by giving off heat to the air passing over the condenser surfaces.

As the hot Freon gas is cooled, it condenses into a liquid at high pressure and accumulates in the receiver. The high pressure liquid Freon passes to the expansion valve at the entrance to the evaporator where it flows through the valve into the evaporator under a much lower pressure. When the Freon is exposed to the lower pressure, it begins to boil and is changed to a vapor state. As the Freon passes through the evaporator, it continues to boil by absorbing heat from the air passing over the evaporator surfaces until it is completely vaporized. From the evaporator the cool low pressure Freon gas is drawn back to the compressor and the cycle repeated.

Thus the air passing over the evaporator surfaces is cooled simply by giving up heat to the Freon during the boiling process.

         Temperature-Pressure Relationship of Freon-12
Degrees F    # Pressure          Degrees F         # Pressure
-40             11.0 *              50                46.7
-35              8.3 *              55                52.0
-30              5.5 *              60                57.7
-25              2.3 *              65                63.7
-20              0.6                70                70.1
-15              2.4                75                76.9
-10              4.5                80                84.1
  5              6.8                85                91.7
  0              9.2                90                99.6
  5             11.8                95               108.1
 10             14.7               100               116.9
 15             17.7               105               126.2
 20             21.1               110               136.0
 25             24.6               115               146.5
 30             28.5               120               157.1
 32             30.1               125               167.5
 35             32.6               130               179.0
 40             37.0               140               204.5
 45             41.7               150               232.0
* Inches of Vacuum

Thus if a gage is attached to a container of Freon-12 and the room temperature is 70° the gage will register a 70 lbs. pressure; in a 100° room, the pressure will be 117 lbs.

Description and Operation of Individual Units

General Description
Cycle of Operation
Compressor
Evaporator
Condenser
Receiver-Dehydrator
Refrigerant Sight Glass
Refrigerant Lines
Blower

General Description

The following general description of the system is intended to familiarize the service man with the location and basic function of the components of the system. The system consists primarily of an evaporator unit and a condensing unit plus other components necessary to obtain proper control and operation of the system. Figure 5 shows the components of the system located in the engine compartment.

The evaporator unit, located under the hood consists of the apparatus to cool the air to the quality desired in the passenger compartment. The evaporator unit includes the housing, evaporator coil and thermostatic expansion valve. The non-adjustable thermostatic switch is attached at the rear of the housing. The blower motor is located on the side of the evaporator housing and directs air from the housing to the air distributor assembly through the heater core located in the dash panel.

The conditioner air duct assembly is mounted on the dash panel inside the passenger compartment and delivers the quantity of conditioned air desired.

Like any refrigeration system, this system, too, must have a condensing unit. A condensing unit may be described as a reclaiming plant since its sole purpose it to reclaim the refrigerant vapor produced in the cooling coil by first compressing and then condensing it into a liquid so that it can be used over and over again. The condensing unit components are located in the engine compartment and consists of the compressor, condenser and receiver-dehydrator.

The prime purpose of the compressor is to convert low pressure refrigerant vapor from the cooling coil into a high pressure, high temperature vapor and direct it to the condenser. It utilizes the principle that "when a vapor is compressed, both its pressure and temperature are raised". The compressor is mounted to the right and above the engine block in a special bracket incorporating rubber bushings. The compressor is "V" belt driven from the engine through an electromagnetic clutch pulley on the compressor.

The purpose of the condenser, as the name implies, is to condense the high pressure refrigerant vapor that is discharged from the compressor. The high pressure, high temperature vapor produced by the compressor is subjected to the considerably cooler metal surfaces of the condenser mounted in front of the radiator and a change of refrigerant state takes place. This is due to the fundamental laws which state that heat travels from the warmer to the cooler surface and when heat is removed from the vapor, a liquid is produced.

The receiver-dehydrator is used primarily as a liquid storage tank, but functions to trap moisture and foreign matter that may have escaped removal during installation or may have entered the system during service operations.

Other components are necessary to obtain proper control and operation of the system. A cooling thermostat, which is mounted on the air duct, has its thermobulb mounted in the distribution air duct. When the thermostatic switch contacts are closed, the clutch actuating coil in the compressor assembly is energized, causing the compressor to operate. When the desired temperature in the car has been reached in accordance with the setting of the thermostatic switch, the switch contacts open and de-energize the clutch coil, releasing the clutch and causing the compressor to stop operating. Due to the raising and lowering of the temperature in the car, the compressor will cycle "ON" and "OFF" as required.

A heater water control valve is mounted in the inlet hot water line on the engine side of the dash panel. The bulb of the control valve is mounted in the discharge air stream. This valve controls the amount of hot water entering the heating coil. Connecting hose lines are required to carry the refrigerant liquid and vapor between the cooling coil and the condensing unit. The smaller hose line is called the high pressure liquid line and the larger hose line connecting the compressor and the cooling coil is the low pressure vapor line. The large hose line between the compressor and the condenser is the high pressure vapor discharge line. A sight glass is located in the high pressure liquid line (as it leaves the bottom of the receiver-dehydrator) for quickly determining whether or not the refrigeration charge is sufficient.

To regulate the amount of air conditioning and/or heat desired, certain controls are required. These are located on the instrument panel and are described under "Controls".

Freon-12 refrigerant is used in the Chevrolet system. It is nonpoisonous (except when in contact with an open flame), noncorrosive (except when in contact with water), noninflammable and nonexplosive. However, the fact that Freon-12, which has a boiling point of 21.7°F below zero at sea level pressure, is contained under pressure appreciably above atmospheric pressure warrants special handling precautions which are described later under "Basic Service Information".

Freon-12 has a definite affinity for oil which greatly assists in the lubricating of the internal parts of the system. The system is lubricated by special Frigidaire oil (525 viscosity) available through parts stock.

Cycle of Operation

Figure 6 presents a schematic arrangement of all the components of the refrigeration system.

Assuming that the control switch is "ON", the thermostat is calling for refrigeration, and the engine and compressor are operating. Low pressure vapor is compressed by the compressor into high pressure vapor and then discharged into the condenser. In the condenser the vapor changes from a high pressure vapor into a high pressure liquid. The liquid then flows into the top of the receiver under pressure.

The high pressure liquid, under pressure, flows through the receiver-dehydrator, which acts as a storage tank as well as a moisture remover, then through the high pressure line which connects to the sight glass, and on to the high pressure connection of the expansion valve.

At the orifice of the expansion valve, the high pressure liquid changes to a low pressure liquid, due to the operation of the compressor, and enters the cooling coil.

Heat enters the conditioning unit housing from the passenger compartment and through the engine compartment by the action of the blower and some leaks through the insulation of the housing itself. Because the cooling coil is colder than the air surrounding it, some of the heat passes through the refrigerated tubes of the coil into the liquid refrigerant. This absorption of heat causes some of the liquid to vaporize and the vapor is drawn through the low pressure line to the compressor.

The lubrication of the internal parts of the expansion valve is brought about by the affinity of Freon-12 for oil, causing them to mix together thoroughly. Even the Freon-12 vapor in a system will carry globules of oil. As the refrigerant travels through the system in either a vapor or liquid state, it is carrying through enough oil picked up in the compressor oil reservoir to keep the moving parts of the valve lubricated. The compressor is lubricated by the action of the compressor oil pump and the oil saturated vapor.

Compressor

Compressor
Hand Shutoff Valves
Compressor Seal
Clutch and Pulley Assembly

Compressor

A five cylinder reciprocating compressor (figures 7 and figure 8) is pivot mounted through an adjustable bracket to the water outlet housing and water pump housing. Intake and exhaust valve reeds at each cylinder effect a definite separation between the discharge (high) side and the intake or suction (low) side of the compressor.

At the rear of the compressor is the compressor head casting which contains the high and low side hand shutoff valve ports and "O" ring gasket seats. In the low side port cavity is a fine mesh intake screen. This screen acts as a filter to prevent the entrance of any undesirable foreign material into the compressor. There is an opening into the high side port cavity for the high pressure relief valve.

The compressor head is mounted to the flange ring on the compressor housing and sealed with a large "O" ring gasket which is partially recessed into the head casting, Provision is made in the bottom of the housing for an oil test fitting.

A high pressure relief valve is provided on the compressor head. Under certain circumstances, the refrigerant pressure on the high side may exceed a safe operating limit. Therefore, to prevent damage to the equipment or the car, the valve is designed to open automatically at approximately 415 pounds per square inch pressure and to close automatically when the pressure is reduced to approximately 300 pounds. Any condition that causes this valve to open should be investigated and steps taken to correct it.

Between the head and the cylinder assembly is the valve plate assembly. On the side of the valve plate facing the compressor head are the five high pressure (discharge) reed valves. On the side of the valve plate assembly facing the cylinder assembly are the five low pressure (suction) reed valves. Under the valve plate and reed assembly is the cylinder assembly which consists of the five cylinders, the needle roller bearing for the main shaft, and the yoke.

A straight mainshaft having different machined diameters for compressor components is supported at one end by the needle roller bearing in the cylinder assembly and by a ball bearing at the front end. The piston and socket plate assembly, which consists of the socket plate assembly, the guide shoe, the piston and rod assembly, the retaining ring and the double row ball bearing, is keyed to the shaft and securely held in place by double set screws. The action of the piston and socket plate assembly can be explained as follows:

As the straight shaft rotates in the needle bearing and in the ball bearing in the bearing holder at the opposite end, the angular bored inner race of the piston and socket plate assembly bearing, which is keyed to the shaft, rotates in the double row bearing causing the socket plate to move in a circular waving motion. The plate assembly is prevented from rotating by the guide shoe which slides in the yoke of the cylinder assembly.

As the pistons are connected to this plate by the piston rods, the pistons will move in and out of the cylinders, resulting in intake to and discharge from the cylinders.

A counter weight is installed on the compressor shaft between the socket plate and the front main ball bearing. The oil pump is located just forward of the mainshaft ball bearing.

The oil is supplied to the oil pump by an oil pick-up tube located along the inside bottom of the compressor shell housing. The oil pump assembly is held in place by a spring wave washer located between the compressor housing and the coil and seal housing.

Another fitting is located on the under side of the compressor shell and is known as an oil test fitting. This fitting consists of a stud which is welded into the compressor shell at the forward end behind the mounting ring and a screw which threads into the stud. The fitting is placed 43 degrees to the side of the vertical centerline. The screw has one hole drilled in the center and another hole drilled at right angles to the center hole just under the screw head. A copper gasket is used to seal the head to the stud. The end of the stud and screw project through the shell and the opening into the screw is at the minimum 4 ounce oil level.

Hand Shutoff Valves (Suction and Discharge Connectors)

The hand shutoff suction and discharge connection valves are individual connectors, connected by a bar and held to the head by a single bolt. The suction and discharge ports are sealed by "O" rings. Located on the suction and discharge connections are gauge fittings for determining both high and low side pressures within the system or compressor. The bodies of the fittings are steel and are threaded at one end for 1/4" flare connections. The other ends are brazed into the body of the hand shutoff valves as shown in Fig. 9.

Both hand shutoff valves should be backseated (turned completely counterclockwise) when the system is in operation and should be turned completely clockwise for removal of the compressor.

NOTE: When attempting to service or remove the compressor or attach gauge lines to the gauge fittings, do not fail to follow directions for the desired procedure as given in this manual. The gauge connections have no Schrader-type core fitting and unless hand shutoff valves are turned completely clockwise before removing the gauge fitting caps all or part of the refrigerant charge may be lost.

Compressor Seal

A compressor shaft seal assembly is used to seal the system from the atmosphere when the compressor is operating or is at rest, regardless of the pressures within the compressor. By this is meant that the system must not leak Freon or oil out of the system or allow air or moisture or dirt to enter the system at any time. The seal assembly which is available for service in a unit package, consists of a rotating shaft seal, a stationary seal seat, an auxiliary shaft seal, "O" rings (2) retainer rings (2) and a seal pin (figures 12, figure 13 and figure 36).

The rotating shaft seal is spring loaded and contains a carbon seat polished to a very flat even surface and an internal "O" ring which contacts the compressor shaft. The stationary seal seat is made of alloy cast iron, which is ground and polished to extreme accuracy. The auxiliary shaft seal is installed over the compressor shaft and within the front cavity of the coil and seal housing. Its purpose is to prevent oil getting into the clutch pulley in the event of a shaft seal leak. An oil drain hole is provided in back of the auxiliary seal to drain any oil trapped by the auxiliary seal through passages in the coil and seal housing and compressor mounting flange to the outside of the system.

A retainer, which serves as the shaft seal rear stop is located just forward of the oil pump cover plate and wave washer which holds the oil pump assembly in position. A drive pin locates in a hole in the shaft near the retainer and engages a keyway in the spring seat of the shaft seal. The front polished carbon face of the shaft seal turns against the ground and polished face of the all-metal stationary seal seat to seal at this point. Seals are also formed by "O" rings between the shaft and the rotating shaft seal, between the front face of the stationary seal seat and the coil and seal housing and between mating surfaces of the coil and seal housing -and the compressor. The auxiliary seal is provided with a spring loaded "V" shaped inner lip to seal between the compressor shaft and front of the coil and seal housing.

If it should become necessary to replace a shaft seal due to a seal leak, all seal components with the possible exception of the pin and retainer rings should be replaced. Extreme care should be used when handling the new parts, to prevent marring or even getting the fingers on the highly polished surfaces of the components.

Clutch and Pulley Assembly

The clutch pulley, which is mounted to the front of the compressor, is driven by a "V" belt drive from a double pulley on the crankshaft of the engine. The clutch is magnetically operated by a clutch actuating coil and clutch armature and operates the compressor when refrigeration is required. The pulley assembly used on 8-cylinder vehicles differs slightly from that used on 6-cylinder vehicles but the clutch mechanism and operation remains the same.

On 6-cylinder vehicles (fig. 13), the pulley consists of the Pulley and Bearing Assembly, which acts as the front clutch pressure plate, and the Clutch Cover Ring which acts as the rear pressure plate. Six screws and lock washers, installed from the rear of the pulley, secure the Cover to the Pulley assembly.

On 8-cylinder vehicles (fig. 12), both the front and rear clutch pressure plates are contained in .the Pulley and Bearing Assembly. This assembly is in two parts, the cover being secured to the front of the pulley by six screws and lock washers. The cover acts as the front pressure plate and the rear part of the assembly contains the rear pressure plate.

The clutch pulley consists of the inner insulating gasket, clutch actuating coil, outer insulating gasket, coil retainer ring and screws, six clutch cover ring bolts and lock washers, pulley assembly including front and rear pressure plates, rear clutch plate to which an armature is riveted, three actuating clutch balls, front clutch plate with a weight attached, three return springs and two shim sets, each consisting of a spacer washer and selected shims.

Assembled to the cast pulley (6-cyl.) or the pulley cover (8-cyl.) is a double row ball bearing and a bearing retainer ring. The pulley is retained to the compressor shaft with a felt backed washer, a lock washer and a nut.

Selective shims installed to the rear of the clutch plate assembly are available as a unit package in three thicknesses .015" .020" and .025" and by proper selection of shims a .005" variation in clearance between the coil and seal housing and the clutch plate armature (rear plate) can be obtained. This clearance should be .025" to .035" when the coil is energized with 12 volts D.C.

Selective shims installed to the compressor shaft forward of the front clutch plate are available in four thicknesses-.010", .015", .020", .025". By proper selection of shims when used with the bearing spacer washer, the proper clearance of .008" to .013" between the frictional material on the clutch plate and the pulley face in the disengaged position may be obtained.

When the clutch actuating coil is energized, the seal housing containing the coil becomes magnetized and attracts the armature on the rear clutch plate which, in turn, causes the clutch plate to move back toward the seal housing. The frictional material on the rear clutch plate contacts the rear pressure plate causing the rear clutch plate to rotate with the pulley. Due to the rotating movement of the rear clutch plate, which is opposed by the force of the three springs, the three clutch balls are caused to roll to the shallow end of the teardrop dimples.

This action forces the front clutch plate to move forward and its frictional material contacts the front pressure plate. The movement of the two clutch plates, one to the rear and the other forward, also causes the clutch actuating springs to be compressed. Since the front clutch plate has the hub locked to the compressor shaft by means of a woodruff key, and the pulley is driven by the V-belt drive from the engine pulley, it follows that with the engine running, the complete clutch assembly will be engaged and turning, and will thus cause the compressor to operate.

When the clutch actuating coil is de-energized, the seal housing containing the coil is de-magnetized. The actuating springs then expand forcing the three clutch balls into the deep depression of the teardrop shaped dimples. This causes the rear clutch plate to move in the direction of the front clutch plate and the front clutch plate to move in the direction of the rear clutch plate, thus causing the frictional material of the front and rear clutch plates to lose contact with the front and rear pressure plates. This permits the pulley to rotate or "free wheel" on the pulley ball bearing without rotating the compressor shaft.

Evaporator Unit

Evaporator Unit
Thermostatic Expansion Valve

Evaporator Unit

Fig. 14< /A>

The evaporator unit is basically a housing containing the cooling coil assembly (evaporator), the thermostatic expansion valve and the blower motor. This unit is mounted to the right fender flange and fender skirt and is joined, by means of a special inlet transition, to the heater core (already part of the Delux heater) and the core case assembly. Thus the heater core becomes an integral part of the air conditioning system. The core, gasket and transition assembly is attached tightly and evenly to the core housing by means of dual camming devices. The cooling coil (evaporator) housing is molded plastic which both insulates the core and resists sweating. The metal blower motor and transition are covered with a coating of expanded plastic which serves the same purpose as well as absorbing sound and providing quieter operation.

As shown in fig. 3 the design, attachment and air flow pattern differ considerably from previous Chevrolet Air Conditioners but still retain the usual ease of installation and maintenance. Air is supplied to the portion of the conditioning unit containing the evaporator by the air duct in the right fender. A "damper", actuated by the "Outside-Inside" air control on the instrument panel opens or closes the duct to supply either outside air or air from inside the car (recirculated air) to the unit.

Thermostatic Expansion Valve

The purpose of the thermostatic expansion valve (fig. 15) is to regulate the supply of liquid refrigerant according to the requirements of the evaporator (cooling coil). In short, it supplies liquid refrigerant to the cooling coil at the same rate that vaporous refrigerant is removed from the coil.

Figure 15 shows a cross-section of the valve which consists primarily of the power element, body, actuating pins (2), stationary seat orifice, needle and needle carriage. At the high pressure liquid inlet is a fine mesh screen which prevents dirt, filings or other foreign matter from entering the valve orifice.

When the valve is connected in the system, the high pressure liquid enters the valve through the screen from the receiver-dehydrator and passes on to the needle seat orifice. The low pressure liquid leaves the orifice and flows into the coil. The low pressure liquid absorbs heat from the coil and changes to a low pressure vapor, and leaves the coil as such. The power element bulb is clamped to the low pressure vapor line just beyond the outlet of the cooling coil (fig. 16).

To produce refrigeration, a pressure dividing point at the valve is necessary. This is where refrigeration begins. The dividing point between high and low temperature and pressure areas in the thermostatic expansion valve is the needle seat and orifice.

The operation of tie valve is quite simple. It is a matter of controlling opposing forces produced by a spring and the refrigerant pressures. For example: The pressure in the power element is trying to push the needle away from the seat, while the adjusting spring is trying to force the needle toward the seat. These opposing pressures are established in the design of the valve so that during idle periods the adjusting spring tension and the refrigerant pressure in the cooling coil are always greater than the opposing pressure in the power element. Therefore, the valve remains closed. This means that the only way the valve can be opened, is to turn the switch at the control panel to the "ON" position, so that the compressor can reduce the pressure and temperature of the refrigerant in the cooling coil. When this pressure is reduced to a point where the vapor pressure in the power element becomes the stronger, the needle moves off the seat and liquid starts to flow through the valve orifice into the cooling coil. As long as the switch on the control panel is on, the thermostat calling for refrigeration, and the compressor operating, the valve will never close and completely shut off the supply of liquid.

The purpose of the power element is to help determine the quantity of liquid that is being metered into the cooling coil. As the temperature of the low pressure line changes at the bulb, the pressure of the vapor in the power element changes, resulting in a change of the position of the valve needle. For example, if the cooling coil gets more liquid than is required, the temperature of the low pressure line is reduced and the resultant lowering of the bulb temperature reduces the pressure of the vapor in the power element allowing the needle to move closer to the seat. This immediately reduces the amount of liquid leaving the valve. Under normal operation, the power element provides accurate control of the quantity of refrigerant to the cooling coil.

Condenser

The condenser (fig. 17) is of all steel brazed construction. Two oval refrigerant tubes form two continuous paths for refrigerant vapor. The adjacent refrigerant passages are joined by a corrugated finned strip that is brazed to the passage plates and serves to increase the effective radiation surface. The inlet manifold connection is 5/8" male flare and the outlet manifold is 5/8" female flare.

The condenser is located in front of the radiator and mounted to the radiator support.

Receiver-Dehydrator

The receiver (fig. 17), which serves as a reservoir for storage of high pressure liquid produced in the condenser, is made of heavy gage drawn steel tube. The receiver also incorporates -a dehydrating agent which is held in the lower portion of the receiver between two screens.

The most important function of the dehydrator is to accumulate moisture that may have escaped removal during the installation or which may have entered the system during service operations. The importance of keeping the interior of the system free of moisture cannot be overemphasized.

The second duty of the dehydrator is to trap foreign matter, such as particles of dirt, copper filings and bits of solder, which may have accidentally remained in the system, so as to keep them from getting through the expansion valve or coil and into the compressor. No service should be performed on the receiver-dehydrator.

Refrigerant Sight Glass

In reality, the sight glass (fig. 17) has no function to perform in the system. By this is meant that the system would operate just as well without it. However, it is a valuable addition to the high pressure liquid refrigerant circuit as it will save a lot of time and eliminate some guesswork in diagnosing difficulties. It provides a quick and sure way of determining whether or not the refrigerant charge is sufficient.

The sight glass has a steel body with the inlet and outlet threaded for 3/8" flare nuts. The refrigerant passes through a small chamber with two small holes which is covered with a sealed glass window. It is so designed that a shortage of refrigerant in the receiver and liquid line will be indicated by the appearance of bubbles or foam 'beneath the glass.

The sight glass is located in the high pressure liquid line at the receiver-dehydrator outlet.

Quick Disconnect Connection

A quick disconnect connection (fig. 18) located in high pressure line just above the sight glass allows the line to be broken without the loss of any of the refrigerant charge. This is especially valuable when components of the refrigeration system must be removed from the vehicle in order to reach and service other units in the engine compartment.

Refrigerant Lines

The components of the system are connected with flexible hoses and couplings. The flexible hoses are constructed with a synthetic material core, which is then covered with a woven metal mesh. This, in turn, is covered by a woven fabric which is coated to protect it from damage. The con. connecting couplings are of the ground seat type. Care must be exercised when making connections to use supporting wrenches at all times. This will require the use of three wrenches, namely, one on the ferrule of the hose, one on the fitting, and one on the mating couplings. The ferrule and the fitting should be held stationary while the coupling is being tightened or loosened. The flexible hoses should not be permitted to come in contact with the hot engine manifold nor should they be bent into a radius of less than 10 times their diameter.

Blower

The blower assembly is mounted on the side of the evaporator unit and consists of a blower wheel and a small motor. The centrifugal or squirrel-cage type blower wheel insures the proper flow of air from the refrigerated area to the ducts leading to the car interior.

The blower wheel is driven by a fractional horsepower, 12 volt, DC, brush-commutator type motor. It is rated at 1/8 HP, has a speed of approximately 3550 RPM (counterclockwise rotation) and will operate within a range of 12 to 14 volts. At full speed the fan has a capacity for moving 150 cubic feet of air per minute.

Basic Service Information

Introduction
Fast Idle Caution
Precautions in Handling Refrigerant Line
Precautions in Handling Freon-12
Maintaining Chemical Stability in the Refrigeration System
Pressure-Temperature Relationship of Refrigerant
Gauge Set
Leak Testing the System
Leak Detector
Vacuum Pump
Availability of Freon-12
Compressor Oil
Compressor Serial Number

Introduction

In any vocation or trade, there are established procedures and practices that have been developed after many years of experience. In addition, occupational hazards may be present that require the observation of certain precautions or use of special tools and equipment. Observing the procedures, practices and precautions of servicing refrigeration equipment will greatly reduce the possibilities of damage to the customers equipment as well as virtually eliminate the element of hazard to the serviceman.

Fast Idle Caution

The 1957 air conditioning equipment includes a hand throttle to permit increasing engine speeds for improved air conditioning while the car is stopped for short periods. A throttle wire guide stop has been provided to limit engine speed to 900 RPM with compressor engaged and transmission in Neutral.

With the fast idle in operation, vehicles equipped with an automatic transmission should be placed in Neutral when stopped.

It is strongly recommended that the transmission be placed in Neutral with the parking brake "ON" whenever it is necessary to run the engine during servicing of the air-conditioning system.

Extreme care should be observed to avoid accidentally shifting Powerglide equipped vehicles into "D", "L" or "R" (or on Turboglide equipped vehicles, "D", "R" or "HR") positions while fast idle is in operation with vehicle standing still.

Adjustment of the fast idle is described under "Service Operations".

Precautions in Handling Refrigerant Lines

• All metal tubing lines should be free of kinks, because of the restriction that kinks will offer to the flow of refrigerant. The refrigeration capacity of the entire system can be greatly reduced by a single kink.
• The flexible hose lines should never be bent to a radius of less than 10 times the diameter of the hose.
• The flexible hose lines should never be allowed to come within a distance of 2 1/2" of the exhaust manifold.
• Flexible hose lines should be inspected at least once a year for leaks or brittleness. If found brittle or leaking they should be replaced with new lines.
• Use only sealed and dehydrated lines from parts stock.
• The use of the proper wrenches when making connections is important. The use of improper wrenches may damage the connection. The opposing fitting should always be backed up with a wrench to prevent distortion of connecting lines or components. When connecting the flexible hose connections it is important that the swaged fitting and the flare nut, as well as the coupling to which it is attached, be held at the same time using three different wrenches to prevent turning the fitting and damaging the ground seat.
• Flares and flare seats should be coated with refrigeration oil before they are assembled to permit the flares to seat squarely and provide for proper tightening. Special thread sealer for refrigerant systems is available from Parts Stock.
• When disconnecting any fitting in the refrigeration system, the system must first be discharged of all refrigerant. However, proceed very cautiously regardless of gauge readings. Open very slowly, keeping face and hands away so that no injury can occur if there happens to be liquid Freon in the line. If pressure is noticed when fitting is loosened, allow it to bleed off very slowly. CAUTION: Always wear safety goggles when opening refrigerant lines.
• In the event any line is opened to atmosphere, it should be immediately capped to prevent entrance of moisture and dirt.
• Flares and flare seats must be in perfect condition. The slightest burr or piece of dirt may cause a leak.
• In the event any line is opened to the atmosphere it should be immediately capped or plugged to prevent the entrance of moisture and dirt. Plastic caps and plugs are supplied in the special tool set for this purpose.

Freon-12 is a transparent and colorless refrigerant in both the gaseous and liquid state. It has a boiling point of 21.7°F below zero and, therefore, at all normal temperatures and pressures it will be a vapor. The vapor is heavier than air and is noninflammable, nonexplosive, nonpoisonous (except when in contact with an open flame) and noncorrosive (except when in contact with water). The following precautions in handling Freon-12 should be observed at all times.

• All refrigerant drums are shipped with a heavy metal screw cap. The purpose of the cap is to protect the valve and safety plug from damage. It is good practice to replace the cap after each use of the drum.
• If it is ever necessary to transport or carry a drum or can of refrigerant in a car, keep it in the luggage compartment. Refrigerant should not be exposed to the radiant heat from the sun for the resulting increase in pressure may cause the safety plug to release or the drum or can to burst.
• Drums or disposable cans should never be subjected to high temperature when adding refrigerant to the system. In most instances, heating the drum or can is required to raise the pressure in the Freon container higher than the pressure in the system during the operation. It would be unwise to place the drum on a gas stove, radiator or use a blow torch while preparing for the charging operation, for a serious accident can result. Don't depend on the safety plug-many drums have burst when the safety plug failed. Remember, pressure can be a powerful force. A bucket of warm water, not over 125°F, or warm wet rags around the Freon container is all the heat that is required.
• Do not weld or steam clean on or near the system. Welding or steam cleaning can result in a dangerous pressure buildup in the system.
• When filling a small drum from a large one, never fill the drum completely. Space should always be allowed above the liquid for expansion. If the drum were completely full and the temperature was increased, hydraulic pressure with its tremendous force would result.
• Discharging large quantities of Freon-12 into a room can usually be done safely as the vapor would produce no ill effects. However, this should not be done if the area contains a flame producing device such as a gas heater. While Freon-12 normally is nonpoisonous, heavy concentrations of it in contact with a live flame will produce a toxic gas. The same gas will also attack all bright metal surfaces.
• Protection of the eyes is of vital importance! When working around a refrigerating system, an accident may cause liquid refrigerant to hit the face. If the eyes are protected with goggles or glasses, no serious damage can result. Just remember, any Freon-12 liquid that you can touch or that touches you is at least 21.7°F. below zero. The eyeballs can't take much of this temperature. If Freon-12 liquid should strike the eyeballs, here is what to do:

1. Keep calm
2. Do not rub the eyes! Splash the affected area with quantities of cold water to gradually get the temperature above the freezing point. The use of mineral, cod liver or an antiseptic oil is important in providing a protective film to reduce the possibility of infection.
3. As soon as possible, call or consult an eye specialist for immediate and future treatment.

REMEMBER-"An ounce of prevention is worth a pound of cure".

Maintaining Chemical Stability in the Refrigeration System

The metal internal parts of the Chevrolet refrigeration system and the refrigerant and oil contained in the system are designed to remain in a state of chemical stability as long as pure Freon-12 plus refrigeration oil is used in the system.

However, when abnormal amounts of foreign materials, such as dirt, air or moisture are allowed to enter the system, the chemical stability may be upset. When accelerated by heat, these contaminates may form acids and sludge and eventually cause the breakdown of components within the system. In addition, contaminates may affect the temperature-pressure relationship of Freon, resulting in improper operating temperature and pressures and decreased efficiency of the system.

The following general practices should be observed to insure chemical stability in the system.

• Whenever it becomes necessary to disconnect a refrigerant or gauge line, it should be immediately capped with a flare plug or cap, depending on the type of connection. Capping the tubing will also prevent dirt and foreign matter from entering.
• Tools should be kept clean and dry. This also includes the gauge set and replacement parts.
• When adding oil, the container should be exceptionally clean and dry due to the fact that the refrigeration oil in the container is as moisture-free as it is possible to make it. Therefore, it will quickly absorb any moisture with which it comes in contact. For this same reason the oil container should not be opened until ready for use and then it should 'be capped immediately after use.
• When it is necessary to open a system, have everything you will need ready and handy so that as little time as possible will be required to perform the operation. Don't leave the system open any longer than is necessary.
• Finally, after the operation has been completed and the system sealed again, air and moisture should be evacuated from the system before recharging.

The chart on page 6 shows us that every time we raise or lower the temperature of a quantity of Freon-12 liquid, we also raise or lower the pressure on it. Unfortunately this is not done in the same ratio. For example, at 70° the chart shows that the pressure is also 70 pounds. But this is true only at 70°. However, if we know the temperature of the liquid in the cooling coil or the receiver, we can refer to a pressure-temperature table and determine what the pressure should be.

The figures can also be used in a reverse manner. If we know what the pressure is at any point in the system we can refer to the pressure-temperature table and determine what the temperature should be.

Gauge Set

The gauge set (fig. 19) is used when purging, evacuating, charging or diagnosing trouble in the system.

The gauge at the right is known as the low pressure gage. The face is graduated into pounds of pressure from 0 to 150 and, in the opposite direction, in inches of vacuum from 0 to 30 inches. This is the gauge that should always be used in checking pressures on the low pressure side of the system. When all parts of the system are functioning properly the refrigerant pressure on the low pressure side never falls below 0 pounds pressure. However, several abnormal conditions can occur that will cause the low pressure to fall into a partial vacuum. Therefore, a low pressure gauge is required.

The gauge at the left is graduated from 0 to 300 pounds pressure. This is known as the high pressure gauge and, of course, is used for checking pressures on the high pressure side of the system.

The connection at the right is for attaching the low pressure gauge line and the one at the left the high pressure gauge line. The center connector is common to both and is for the purpose of attaching a line for adding refrigerant, discharging refrigerant, evacuating the system and other uses. When not required, this line or connection should be capped.

NOTE: Gauge fitting connections should be installed hand tight only and the connections leak tested before proceeding.

The hand shutoff valves on the gauge manifold do not control the opening or closing off of pressure to the gauges. They merely close each opening to the center connector and to each other. During most diagnosing and service operations, the valves must be closed. The only occasion for opening both at the same time would be to bypass refrigerant vapor from the high pressure to the low pressure side of the system, or in evacuating both sides of the system.

A temperature scale for Freon-12 (yellow band) has been provided on the gauges. The temperatures on this scale are in correct relationship to the pressures on the outside (white) pressure band, providing a quick and convenient pressure temperature relationship reference for Freon-12.

Leak Testing the System

Testing the system for refrigerant leaks is accomplished with a leak detector, Tool 6084, a propane gas-burning torch (fig. 20) which is described below under "Leak Detector."

Whenever a leak is suspected in the system or a service operation performed which results in disturbing lines or connections, it is advisable to test for leaks. Common sense should be the governing factor in performing any leak test, since the necessity and extent of any such test will, in general, depend upon the nature of the complaint and the type of service performed on the system. It is better to test and be sure, if in doubt, than to risk the possibility of having to do the job over again.

Leak Detector

Leak Detector
Assembling Detector
Operating Detector
Servicing the Leak Detector

Leak Detector

Tool 6084 (fig. 20) is a propane gas-burning torch which is used to locate a leak in any part of the Freon system. Freon gas drawn into the sampling tube attached to the torch will cause the torch flame to change color in proportion to the size of the leak. Propane gas fuel cylinders used with the torch are readily available commercially throughout the country.

CAUTION: Do not use lighted detector in any place where combustible or explosive gases, dusts or vapors may be present.

Assembling Detector

1. Remove dust cap from cylinder.
2. Thread detector unit onto top of fuel cylinder. Turn to right (clockwise) until the unit is HAND TIGHT-IT. Do not use a wrench to tighten.
3. Check valve knob to be sure it is in fully closed position.
4. Assemble sampling hose to detector unit.

1. Open control valve only until a low hiss of gas is heard, then light gas at opening in chimney.
2. Adjust flame until desired volume is obtained. This is most satisfactory when blue flame is approximately 3/8" above reaction plate. The reaction plate will quickly heat to a cherry red.
3. Explore for leaks by moving the end of the sampling hose around possible leak points in system (fig. 21). Do not pinch or kink the hose. NOTE: Since Freon-12 is heavier than air, it is good practice to place open end of sampling tube immediately below point being tested, particularly in cases of small leaks. CAUTION: Do not breathe the fumes that are produced by the burning of Freon gas in the detector flame, since such fumes can be toxic in large concentrations of Freon.
4. Watch for color changes. The color of the flame which passes through the reaction plate will change to yellow when sampling hose draws in very small leaks of Freon-12. Large leaks will he indicated by a change in color to a vivid purplish-blue. When the sampling hose passes the leak, the flame will clear to an almost colorless pale-blue again. NOTE: If the flame remains yellow when unit is removed from leak, insufficient air is being drawn in or the reaction plate is dirty. See "Servicing the Leak Detector" below.

Insufficient Air

Insufficient air may be caused by:

1. Obstructed or partially collapsed sampling tube.
2. Dirt or foreign substance in burner tube.
3. Dirty or partially clogged orifice.

Blowing air through the sampling hose and back through the detector will usually clear dirt or foreign matter.

Dirty Reaction Plate

If a continuous yellow flame is caused by a dirty reaction plate, allow the flame to burn for several minutes. This will usually burn the plate clean. If an oxide film appears on the reaction plate from continued use, it will reduce the sensitivity of the detector. This may be remedied by removing the plate, which is attached to the chimney with a signal screw, and scraping the surface gently with a knife.

Dirty or Partially Clogged Orifice

NOTE: Never attempt to clean orifice by passing anything through the hole.

1. Unscrew burner head assembly from burner tube connecting head to valve assembly. Use a wrench if necessary.
2. Remove orifice from tube. 3
3. Reverse orifice and screw burner head onto burner tube hand tight.
4. With unit connected to propane cylinder, open valve quickly, admitting several short blasts.
5. Unscrew burner head, insert orifice into burner tube in normal position and screw burner head onto burner tube. Tighten with a wrench to form a gas-tight joint.

A vacuum pump should be used if available for evacuating air and moisture from the 1957 Chevrolet Air Conditioning System.

Vacuum pump, Tool 5428, (fig. 22) is available for this purpose and its use is described under "Service Operations". The following precautions should be observed relative to the operation and maintenance of this pump.

• Install Tool 5462-1 to vacuum pump to prevent pressure from entering pump (see Figure 25).
• Make sure dust cap on discharge outlet of vacuum pump is removed before operating.
• Check oil level frequently. Oil level should be up to the oil level screw on the side of the vacuum pump (fig. 22). Do not maintain fluid above this level as the pump will not operate properly.
• When adding oil, use only Frigidaire 150 viscosity oil. Carefully pry off top cover of pump and add oil as shown in Figure 23 to bring to proper level.
• Change oil periodically. Remove compressor top and lay on side, holding rotor in place while draining. Rotor and eccentric can be replaced by rotating slowly to align eccentric and then lower gently into place.
• Cap suction and discharge ports when not in use.
• Do not use the vacuum pump as an air compressor.
• If pump does not start, check the capacitor and relay. Also, the top may be removed and the rotor turned by hand to relieve a temporary

Freon-12 is available through Parts Stock in 25 lb. drums and in 15 oz. disposable cans. Valves are available for the disposable cans, which may be used as individual cans or as a group of three cans connected in series (fig. 24).

Tool 6272 is used with the three cans connected in series. The use of the three-can fixture makes it possible to charge the system with a known quantity of refrigerant (45 oz.) without the use of weighing equipment necessary with the larger drum. The single can valve 6271 can be used for completing the charge and for miscellaneous operations such as flushing. The valves are installed by piercing the top seal of the cans.

Compressor Oil

A special refrigeration lubricant, Frigidaire 525 viscosity oil (fig. 25), should be used in the system. It is available in 1 quart graduated bottles through Parts Stock. This oil is as free from moisture and contaminants as it is possible to attain by human processes. This condition should be preserved by immediately capping the bottle when not in use.

The total lubricant capacity of the compressor is 9 ounces (avoirdupois).

Due to the porosity of the refrigerant hoses and connections, the system refrigerant level will show a definite drop after a period of time. Since the compressor oil is carried throughout the entire system mixed with the refrigerant a low refrigerant level will cause a dangerous lack of lubrication. Therefore the refrigerant charge in the system has a definite tie-in with the amount of oil found in the compressor and an insufficient charge may eventually lead to an oil buildup in the evaporator.

Compressor Serial Number

The compressor serial number is located on the serial number plate on top of the compressor. The serial number consists of a series of numbers and letters (Example: 10-CC-001). This serial number should be referenced on all forms and correspondence related to the servicing of this part.

Inspection and Periodic Service

Pre-delivery Inspection
1000 Mile Inspection
Periodic Service

Pre-delivery Inspection

1. Check the belt for proper tension.
2. With controls positioned for operation of the system, operate the unit for ten minutes at approximately 1500 RPM with the clutch actuating coil energized. It may be necessary to use a jumper wire to the hot side of the battery to accomplish this. Observe the clutch pulley bolt to see that the compressor is operating at the same speed as the clutch pulley. Any speed variation indicates clutch slippage.
3. Check the sight glass to see that the unit has a sufficient Freon-12 charge. Bubbles in the flow indicate a low charge. No liquid visible indicates no charge.
4. Leak test the complete system.
5. If there is evidence of an oil leak, check the compressor to see that the oil charge is satisfactory.
6. Check the system controls for proper operation.

1. Check unit for any indication of a refrigerant leak.
2. If there is an indication of an oil leak, check the compressor for proper oil charge.
3. Check sight glass for proper charge of Freon-12. This should only be done after running unit at approximately 1500 RPM for ten minutes with controls positioned for operation of the system. The clutch actuating coil must be energized. Use a jumper wire to the hot side of the battery to accomplish this, if necessary.
4. Tighten the compressor brace and support bolts and check the belt tension.

• Inspect condenser and radiator cores at 2000 mile intervals to be sure that they are not plugged with leaves or other foreign material.
• Check evaporator drain tubes at 2000 mile intervals for dirt or restrictions.
• At least once a year, check the system for proper refrigerant charge and the flexible hoses for brittleness, wear, or leaks.
• Every 2000 miles check sight glass for low Freon level.
• Check belt tension

Performance Test
Diagnosis
Diagnosis Summary

Performance Test

This test may be conducted to determine if the system is performing in a satisfactory manner and should be used as a guide by the serviceman in diagnosing trouble within the system.

The following fixed conditions must be adhered to in order to make it possible to compare the performance of the system being tested with the standards below.

1. Doors and windows closed.
2. Hood up.
3. Controls set for full outside air, "M" blower, and maximum cooling (COLD lever in full down position). HEAT control must be in "off" or full "up" position.
4. Engine running at 1500 RPM.
5. Vehicle in neutral and an 18" fan in front of condenser radiator.
6. System settled out (run in approximately 10 minutes).
7. Compressor hand shutoff valves fully count.

The following performance data define normal operation of the system under above conditions. The temperature and pressure differential shown indicate differences which may be expected due to humidity variations.

                             70º       80º     90º      100º
Minimum Right 
Discharge Temperature      45º-52º   45º-54º  46º-56º  48º-60º 
Maximum Head Pressure      140-160   145-220  190-250  210-280 
Minimum Suction Pressure    16-22     20-28    21-31    22-35 

Whenever trouble develops in the refrigeration system, the diagnosis procedure listed below for the particular condition encountered, will assist in locating the source of trouble.

Symptoms and Probable Cause
Diagnosis Procedures

Drafts

A. Poor air distribution.
a. Readjust air outlets.

B. Car temperature too low.
a. Check thermostatic switch for stuck closed points and improper thermobulb location.
b. Check control panel linkage.
c. Check clutch pulley for constant engagement.

Shortage of Air Supply at Outlets

A. Car temperature up.
a. Check position of air dampers. HEAT lever should be in UP position and OUTLET lever in DOWN position.
b. Check fan speeds.
c. Check cooling coil for air passage.

B. Low fan speed.
a. Check voltage at fan motor.
b. Check motor bearings.
c. Check direction of motor rotation.

Air Noise

A. Sharp obstruction in air stream.
a. Check internal surfaces of ducts and smooth out kinks or rough edges.

B. Small slits in ducts.
a. Check ducts and close all holes or openings.

C. Obstruction in outlets or ducts.
a. Check for partly covered outlets, loose materials in ducts or fan housing and loose dampers in ducts.

Scraping Noise

A. Fan hitting fan housing.
a. Adjust fan to turn free on all sides.
b. Check motor bearings.
c. Tighten motor mountings.

Rattle and Vibration Noises

A. Loose ducts, tubing or compressor
a. Check duct, tubing clamps, compressor and compressor mounting for looseness and tighten where required.

B. Cooling coil mounting bolts loose.
a. Tighten or install new bolts.

Water Leaking or Dripping Into Passenger Compartment

A. Drip pan or drain tubes stopped up.
a. Clean drip pan and drain tubes.

B. Housing sweating.
a. Check insulation in housing.

Hissing Noise at Expansion Valve

A. Shortage of refrigerant (indicated at sight glass).
a. Locate and repair leak and add refrigerant.

B. Restriction in liquid line.
a. Check receiver-dehydrator for partial stoppage.
b. Check line for kinks.
c. Check filter screen at expansion valve.

Partial Frosting and Sweating of Cooling Unit or Poor Cooling

A. Improperly installed or adjusted controls.
a. Check all controls for proper installation and adjustment, particularly linkage to thermostatic
switch and heater control valve.

B. Heater valve does not cut off circulation of the engine coolant through the heater core with HEAT control in "off" position (poor cooling).
a. Check temperature of copper tube entering conditioning unit below upper heater hose. Coolant from control valve flows through this tube and if hot coolant flow is indicated, adjust controls or replace valve.

C. Shortage of refrigerant (indicated at sight glass).
a. Locate and repair leak and add refrigerant.

D. Restricted or clogged liquid line.
a. Check receiver-dehydrator for partial stoppage.
Check line for kinks.

E. Thermostatic switch malfunctioning.
a. Replace thermostatic switch.

F. Expansion valve malfunctioning.
a. Replace expansion valve.

Failure to Cool

A. Heater valve does not cut off circulation of the engine coolant through the heater core with HEAT control in "off" position.
a. Check temperature of copper tube entering conditioning unit below upper heater hose. Coolant from heater control thermostat flows through this tube and if hot coolant flow is indicated, adjust controls or replace valve.
B. Faulty thermostatic switch operation.
a. Check linkage from control panel to thermostatic switch for proper installation and adjustment.
b. Check fuse.
c. Check thermostatic switch bulb location.
d. Check thermostatic switch contacts and terminal connections.
e. Check clutch actuating coil connections and coil.
f. Check switch adjustment and adjust thermostatic setting if necessary.

C. Faulty clutch operation.
a. Check clutch for slippage by watching bolt in center of compressor shaft. Bolt should be turning at same speed as pulley.
b. Check for belt slippage.
c. Check air gap which should be .025" to .035".
d. Remove and check internal parts of clutch and replace where necessary. Check and adjust all shims as required.

D. Lost refrigerant charge (complete charge).
a. Locate and repair leak, process and charge system and check for proper oil level.

E. Blower not operating properly.
a. Check electrical circuit.
Check motor and fan.

F. Insufficient air.
a. Check that OUTLET lever is in DOWN position.
b. Check motor speed.
c. Check for restrictions in ducts.
d. Check for dirty coils (refrigeration and heating).
e. Remove coils to clean as necessary.

G. Stopped up liquid line or receiver dehydrator.
a. Check for stoppage and replace if necessary.

H. Faulty expansion valve.
a. Expansion valve malfunctioning. Replace valve as required.
b.Discharged power element. Replace valve.
c. Stopped up expansion valve filter screen.
d. If screen cannot be cleaned, the valve must be replaced.

Intermittent Failure to Cool

A. Freeze-up in high humidity areas.
a. Raise low limit of thermostatic switch.

Too Cool

A. Faulty thermostatic switch.
a. Check control panel linkage to switch, and adjust if necessary.
b. Check location of switch thermobulb.
c. Check contacts in switch.
d. Replace thermostatic switch if necessary.

B. Faulty clutch.
a. Check for stuck clutch.
b. Remove and disassemble pulley, check parts and replace where necessary.

High Gauge Reading on High Side of System

A. Air or excessive refrigerant in system
a. Check complete system for leaks. Where detected, discharge system, repair leaks, then evacuate and recharge system with a complete charge.

B. Blocked air circulation through condenser.
b. Clean condenser with stiff brush, compressed air or cool water. Never use steam!

C. High engine temperature.
c. Perform required engine maintenance.

Low Gauge Reading on High Side of System

A. Shortage of refrigerant.
a. Check for shortage, locate leak and repair.
b. Add refrigerant as required.

B. Faulty compressor.
a. Replace serviceable parts or compressor.

High Gauge Reading on Low Side of System

A. Clutch slipping.
a. Check clutch and make necessary repairs.

B. Excessively high head or high side pressure.
a. Check system for leaks. Discharge system, repair any leaks found, then evacuate and recharge system.

C. Over-feeding of expansion valve.
a. Check expansion valve for poor bulb contact to suction line.
b. Replace valve if necessary.

D. Faulty compressor.
a. Replace compressor if found to be faulty.

Low Gauge Reading on Low Side of System

A. Shortage of refrigerant.
a. Check for leak, repair leak and recharge system.

B. Clutch will not disengage.
a. Check thermostatic switch controls, contacts and bulb location.
b. Remove clutch pulley and replace internal parts of clutch if necessary.

C. Restriction in liquid line, suction line, receiver-dehydrator or screen at expansion valve.
a. Check lines for kinks and replace lines if kinks are found.
b. Check receiver-dehydrator. If partly stopped up, it will be cold or frosted.
c. Check expansion valve. If partly stopped up, it will be cold or frosted.

D. Cooling coil dirty or iced up.
a. Check cooling coil. If dirty, clean coil with cold water. If iced up defrost coil and check thermostatic switch and expansion valve.

Diagnosis Summary

High Head Pressure Indications

a. Air in system or overcharge of refrigerant.
b. Blocked air circulation through condenser.
c. High condensing medium temperature.

Low Head Pressure Indications

a. Restricted expansion valve.
b. Faulty compressor-will not pump.
c. Shortage of refrigerant.
d. Low condensing medium temperature.

Shortage of Refrigerant Indications
a. Hissing noise at expansion valve.
b. Sight glass shows bubbles or foam.
c. High coil temperature.
d. Low head pressure.
e. Very little or no sweating.

Continuous Operation of Compressor Indications

a. Low car temperature.
b. Coil icing or heavy frost.
c. Coil icing or heavy frost and high car temperature.
d. Defective clutch or thermostatic switch.

Poor or No Refrigeration Indications

a. Control panel linkage to water control valve or thermostatic switch not installed or adjusted
properly.
b. Shortage of refrigerant.
c. Improper adjustment of thermostatic switch.
d. Expansion valve set too high or open too wide.
e. Expansion valve setting not high enough to use maximum surface of cooling unit or not open
enough.
f. Expansion valve bulb improperly located.
g. Discharged thermobulb on expansion valve.
h. Expansion valve needle leaking-not seating properly.
I. Faulty compressor-will not pump.
j. Heavy coating of frost or ice on cooling coil.
k. Partially stopped up receiver-dehydrator, liquid line or suction line.
1. Excessive head pressure.
m. High condensing medium temperature.
n. Clutch slipping.
o. Clutch actuating coil not operating.

Needle Stuck Open in Expansion Valve

a. Frosted or sweating suction line.
b. Poor refrigeration.
c. High head pressure.

Needle Stuck Shut in Expansion Valve

a. No cooling.
b. Very low back pressure reading.
c. No refrigeration in cooling unit.

Service Operations

Conditioning System for Replacement of Component Parts
Installing Gauge Set to Check System Operation
Purging the System
Evacuating the System
Adding Refrigerant
Vacuum Pump Method of Evacuating an Charging the System
Compressor Method of Evacuating and Charging the System
Checking and Adding Oil
Air or Excessive Refrigerant in the System
Expansion Valve
Sight Glass Replacement
Receiver-Dehydrator Replacement
Condenser Replacement
Refrigerant Line Replacement
Evaporator Unit
Compressor Replacement
Compressor Head and/or Valve Replacement
Clutch Pulley Assembly
Clutch Actuating Coil Replacement
Compressor Seal Replacement
Pressure Relief Valve
Collision Procedure
Compressor Belt Replacement and/or Tension Adjustment
Blower Motor Replacement
Thermostatic Switch
Control Adjustments
Heater and Defroster Components

Conditioning System for Replacement of Component Parts

Air conditioning, like many other things, is fairly simple to service once it is understood. However, there are certain procedures, practices and precautions that should be followed to prevent costly repairs, personal injury or damage to equipment. For this reason it is strongly recommended that the preceding information in this section, particularly "Basic Service Information", be studied thoroughly before attempting to service the Chevrolet System.

In removing and replacing any part in the refrigeration system, the following operations, which are described in this section must be performed in the sequence shown.

1. Purge the system by releasing the Freon to the atmosphere. If only the compressor is to be removed the rest of the system need not be purged (see compressor Replacement Removal).
2. Remove and replace the defective part.
3. If only the compressor has been purged and removed only the compressor needs to be evacuated (see Compressor Replacement Installation) otherwise the entire system must be evacuated.
4. Charge the system with Freon-12. If only the compressor has been replaced and evacuated according to instructions no Freon need be added to the system (see Compressor Replacement-installation).

NOTE: Tool 5427, for operating the compressor hand shutoff valves, may be difficult to use because of the restricted space around the valves. If desired, the end of the tool may be cut off and a new hole drilled for the handle. This will reduce its size enough to allow its use in a much smaller area. A 1/4" ratchet type wrench, Tool 6105, available from the Kent Moore organization, is a very useful tool for this application.

CAUTION: Always wear protective goggles when working on refrigeration systems. Goggles 5453 are included in the set of air conditioning special tools. Also, beware of the danger of carbon monoxide fumes by avoiding running the engine in closed or improperly ventilated garages.

Installing Gauge Set To Check System Operation

1. With engine stopped, remove air cleaner.
2. Turn hand shutoff valves fully counterclockwise, remove caps from high and low pressure compressor gauge fittings.
3. Connect gauge lines to gauge fittings fig. 26.
4. Purge air and moisture from gauge lines by the following method:
   • Uncap the center line of the gauge set slightly.
   • Turn the high pressure compressor hand shutoff valve 1/4 turn clockwise and the high side gauge valve 1/4 turn counterclockwise.
   • Allow gas to hiss through the center line cap for three seconds.
   • Tighten cap on the gauge center line and close the high side gauge valve.
   • Follow the same procedure for the low pressure compressor hand shutoff valve and the low side gauge valve.

In replacing any of the air conditioning components the system must be completely purged or drained of refrigerant. The purpose is to lower the pressure inside the system so that a component part can be safely removed.

1. With engine stopped and compressor hand shutoff valves positioned for normal operation (fully counterclockwise) remove air cleaner and install high and low pressure lines of gauge set to high and low pressure gauge outlets on compressor (see Installing Gauge Set to Check System Operation Steps 1-4).
2. Open both compressor hand shutoff valves 1/4 turn clockwise.
3. With plug removed from the centerline on the gauge manifold, open high pressure gauge valve and discharge the vapor slowly through the center connection. CAUTION: Do not open valves too much or compressor oil may be discharged with the Freon. A rag wrapped around the end of the center gauge line will prevent the splashing of oil in the event of accidental rapid discharge.
4. When the pressure is reduced to below 100 pounds on the high pressure gauge, open the low pressure gauge valve and continue discharging until all refrigerant has been released or the pressure does not exceed 5 pounds. Close both gauge valves.
5. Close both compressor hand shutoff valves by turning fully clockwise. The complete system has now been purged of Freon and any part in the system can be replaced.

Whenever the air conditioning system is opened for any reason, it should not be put into operation again until it has been evacuated to remove air and moisture which may have entered the system. There are two methods which may be used to evacuate the system.

The preferred method is to connect a vacuum pump, Tool 5428, into the system as shown in fig. 27. If no vacuum pump is available, the second method is to make use of the compressor to evacuate the system as shown in fig. 28.

Adding Refrigerant

Adding Refrigerant
Partial Charge

Adding Refrigerant

An important rule to follow in charging is that refrigerant should always be added to the compressor in a vaporous state. Another important rule is never to add refrigerant until the system has been leak tested and properly processed.

In order to charge refrigerant in the vapor state, the Freon-12 container will require the use of some heat. This can best be accomplished by placing the drum or cans in an upright position in a bucket or container of warm water. The temperature of the water should not exceed 125°F. Since the temperature of the water and drum or cans will decrease, as the vapor leaves the containers, the water and containers will be cooled. This may result in a lowering of the container pressure to the extent where it may be necessary to replenish or reheat the water unless an adequate amount of water is used.

With the compressor in operation, the head pressure should not exceed 275 lbs. and the pressure within the Freon containers should always be maintained at a minimum of 12 pounds and should not exceed a maximum of 90-100 pounds. When the low side valve on the gauge set is closed, the gauge will then indicate the low side pressure in the compressor. When the low side valve on the gauge set is open, the gauge indicates drum pressure. Refer to "Basic Service Information" for a description of gauge set valve operation.

Vacuum Pump Method for Evacuating and Charging

1. With the system completely purged, install the high and low pressure lines of the gauge set to the gauge fittings on the compressor if this has not previously been done. Each hand shutoff valve should be positioned 1/4 turn clockwise from the full counterclockwise position.
2. Install center gauge line to tee connector Tool 5462-2.
3. Install female connector (Tool 5462-7) at the inlet side of the vacuum pump.
4. Insert flare seat (Tool 5462-8) into connector 5462-7 at the vacuum pump.
5. Install shutoff valve (Tool 5462-1) to the connector at the vacuum pump.
6. Install a gauge line from one side of tee connector to the valve at the vacuum pump. The valve should be closed.
7. Install the gauge line from the remaining tee connection to a drum of Freon-12 or to 3 full cans of Freon-12 in Tool 6272. When using a drum, it will be necessary to use fitting (Tool 5462-9) and reducer (Tool 5462-4) with lead washer (Tool 5462-3) between the gauge line and drum.
8. Check level of fluid in vacuum pump and add Frigidaire 150 viscosity oil if necessary to bring to proper level. Also make sure dust cap on discharge side of vacuum pump has been removed. NOTE: Information on servicing the vacuum pump in event of low fluid level or failure to start is described under "Basic Service Information."
9. Open high and low pressure gauge valves. CAUTION: Shutoff valve at vacuum pump must be closed. If pressure enters pump, cover may blow off.
10. Start the vacuum pump and slowly open the hand shutoff valve at the pump to avoid forcing oil out of the pump. A vacuum is now being drawn on both the high and low pressure sides of the system at the same time. NOTE: If oil is blown from the pump, it should be refilled to proper level with Frigidaire 150 viscosity oil as described under "Basic Service Information."
11. Operate the pump to obtain approx. 28" vacuum for 10 minutes. If approx. 28" vacuum cannot be obtained, close the shutoff valve at the pump and stop the pump. Note the low pressure gauge to see if the vacuum holds. If the vacuum holds, the pump or gauge may be faulty. If vacuum will not hold, open refrigerant cylinder valve to charge system to cylinder pressure and check system and gauge hookup for leaks with leak detector, Tool 6084. After locating leak, discharge system of Freon, repair leak and repeat operation to obtain approx. 28" vacuum for 10 minutes.
12. Close hand shutoff valve at pump, stop pump and observe low pressure gauge to see that 28" of vacuum holds for 3 minutes. If vacuum does not hold, check for leaks as described in Step 11. If vacuum holds or if any leaks found have been repaired, proceed with Step 13.
13. Open the Freon container valve to charge the system to cylinder pressure, then close valve.
14. Discharge system, then evacuate the system again at approx. 28" vacuum for 10 minutes. This second evacuation is to remove any air or moisture that may have remained in the system.
15. Close gauge valves. The system is now ready for a complete charge (4 lbs. Freon-12). Do not remove the gauge connections but proceed with the charging operation.

Complete Charge-Vacuum Pump Method

If the entire charge of refrigerant has been lost through accident or in the replacement of any of the components, a complete charge will be necessary and should be added after evacuation as described below.

1. With gauge set, adapters and Freon drum (or cans) installed as shown in Figure 27, make sure high and low pressure gauge valves and the valve on the Freon drum are closed.
2. Open low pressure gauge valve.
3. If using a drum of Freon place drum on scales and weigh accurately. This is to determine amount of Freon used. Set drum (or cans) in pail of water heated to not more than 125°F. If pail of water is used, weigh it with Freon drum. NOTE: If the disposable cans of Freon are used, the scales can be eliminated since the contents of 4 1/4 of the cans will comprise a complete charge of refrigerant for the system. When charging from cans, put four cans into system and as much of the fifth as needed for sight glass to run clear. See "Basic Service Information" for availability of Freon-12.
4. Open the valve wide on the Freon drum or 3 can fixture. Freon-12 vapor under pressure will flow into the system without operating the compressor. This amount should not exceed 4 lbs. Close low pressure valve in gauge set at frequent intervals to be certain pressure in the low side is always maintained above 12 lbs. NOTE: If it is not possible to charge the entire 4 lbs. by this method, then operate the engine and compressor at 1000 rpm minimum to complete the charging operation. To insure operation of the compressor during charging, the clutch actuating coil can be energized by connecting a wire from the battery positive terminal to the coil. The pulley nut on the end of the compressor shaft will rotate with the compressor engaged.
5. When 4 lbs. of Freon have entered the system, close the Freon container valve and the low pressure gauge valve. The engine can be operated at 1500 RPM to observe high and low pressure gauges as well as sight glass and general performance of the system.
6. Stop engine and back seat both compressor hand shutoff valves fully counterclockwise.
7. Remove the gauge set and jumper wire, replace caps on gauge fittings and shutoff valves and install air cleaner.

1. Have gauge set and Freon drum or cams connected as shown in Figure 28. Before attaching gauge fittings be sure compressor hand shutoff valves are turned fully counterclockwise.
2. Turn compressor high pressure hand shutoff valve fully clockwise and low pressure hand shutoff valve 2 turns clockwise.
3. Open high pressure gauge valve and loosen the connection at the center gauge fitting.
4. Install a jumper wire between hot side of battery and clutch coil, then start engine and allow to run at idle to obtain a vacuum of approx. 28" for five minutes. NOTE: Position a container to receive any oil discharged from the center gauge connection so that an equivalent amount of new oil may be added to the compressor.
5. While engine is running close high pressure gauge valve.
6. Stop engine and observe if 28" vacuum will hold for 3 minutes. NOTE: If vacuum will not hold, either a leak is present in the system or the compressor (being used as a vacuum pump) is at fault. Test system for leaks after first charging to drum pressure. If no leaks are found elsewhere the compressor is at fault.
7. Open valve on Freon drum or cans and allow gas to hiss through loosened center connection at gauge fitting for 2 seconds. Then tighten center gauge connection. Open low pressure gauge valve and allow system to charge up to drum pressure. Close valve on Freon drum or can and close low pressure gauge valve.
8. Open high pressure gauge valve and loosen center gauge fitting, again purging the system by allowing the Freon charge to hiss out. After system is purged start engine and allow to run at idle to obtain a vacuum of approx. 28" for 5 minutes.
9. While engine is running close high pressure gauge valve and stop the engine. NOTE: This second evacuation is to eliminate any air or moisture which may have remained in the system.
10. Again purge center gauge line by opening the valve on the Freon drum and allowing the gas to hiss out the loosened center gauge connection for two seconds. Then tighten the connection.

The system is now ready for complete charge (4 lbs. Freon-12). Do not remove gauge set or jumper wire after evacuation, but proceed with charging operation.

Complete Charge-Compressor Method

1. With gauge set and Freon drum (or cans) installed after evacuation as shown in Figure 28, make sure that gauge valves are closed, the valve on Freon drum (or cans) is closed and the compressor high pressure shutoff valve is closed. The compressor low pressure hand shutoff valve should be opened 2 turns.
2. Place Freon drum on scales and weigh accurately. This is to determine amount of Freon used. Set drum in pail of water heated to not more than 125 deg F. if desired. (if pail of water is used, weigh it with Freon Drum.) NOTE: If the disposable cans of Freon are used the scales can be eliminated since the contents of 4 of the cans (64 oz.) will comprise a complete charge for the system.
3. Open the low pressure gauge valve and the valve on the Freon drum or cans. Freon-12 vapor under pressure will flow into the system without operating the compressor. The amount charged should not exceed 4 lbs. Close the low pressure shutoff valve to be certain that the pressure in the low side is always maintained about 12 lbs. NOTE: If it is not possible to charge the entire 4 lbs. of Freon by this method, open the compressor high pressure shutoff valve 2 turns and operate the engine and compressor at 1000 RPM minimum to complete the charging operation.
4. When 4 lbs. of Freon have entered the system close the Freon drum valve and the low pressure gauge valve. The engine can be operated at 1500 RPM to observe high and low pressure gauges as well as sight glass and general performance of the system.
5. Turn both compressor hand shutoff valves fully counterclockwise to return them to normal operation, remove the gauge set and jumper wire, replace caps on gauge fittings and hand shutoff valves and install air cleaner. NOTE: Be sure to return hand shutoff valves to normal operation before removing gauge lines.

This operation is performed when a shortage of refrigerant is noted without any evidence of leakage or necessary part replacement. Always leak test the system before adding a partial charge.

In some instances it may be more advantageous to purge all refrigerant from the system and add a complete charge than to replenish smaller losses in the system. This may be particularly true in cases where Freon-12 is stocked in disposable cans or scales are not available. The following procedure for adding a partial charge may be used where suitable scales are available.

1. With engine stopped, remove both hand shutoff valve caps, making sure that both valves are in extreme counterclockwise position.
2. Remove air cleaner and connect gauge set, adapters and Freon drum (or can) to compressor as shown in Figure 29. Both gauge valves should be closed and the center gauge line should be left loose at connection to Freon container to permit purging of the lines.
3. Turn both hand shutoff valves 1/4 turn clockwise.
4. Open both valves (in turn) on the gauge manifold 1/4 turn counterclockwise to permit refrigerant vapor to pass from high and low side of compressor into gauge lines and manifold and out loosely threaded end of center gauge line forcing refrigerant vapor, air and moisture out of the lines. Allow vapor to escape for a few seconds, then tighten center gauge line connection and close gauge valves fully by turning clockwise.
5. Place a jumper wire between battery positive terminal and coil hot lead and operate the engine and compressor at slow idle.
6. Place Freon drum (or can) in a container of warm water (125°F. max.) on a scale and note scale reading. Open Freon container valve and low pressure gauge valve to allow Freon to enter the system. Start engine and run at 1000 minimum RPM. When a solid column appears without bubbles in the sight glass, close Freon container valve and note scales to determine amount of refrigerant charged into system.
7. Open Freon container valve and proceed to charge an additional 1/2 lb. of Freon-12 into the system. Close the Freon container and low pressure gauge valves. CAUTION: Do not charge more than 4 lbs. of Freon-12 into the system at any time.
8. Operate the engine at 1500 RPM and observe the gauges, sight glass and entire system for proper performance.
9. After 5 minutes of operation, again check the sight glass. If bubbles are still visible, add refrigerant until sight glass clears and check scales.
10. When satisfied with the operation, shut off engine and turn compressor hand shutoff valves fully counterclockwise.
11. Remove jumper wire and gauge connections at compressor. Install air cleaner and all protective caps.

Compressors are originally fully charged with 9 ounces of Special Frigidaire 525 viscosity oil. If a refrigerant leak is found which indicates some loss of oil by the presence of oil around the leak, or if it is necessary to determine whether or not the compressor has a sufficient amount of oil, the following procedure should be used after making necessary repairs.

Checking Oil Level

1. Set controls for maximum output of air conditioning system and operate engine and compressor at slow idle for 5-7 minutes. Stop engine.
2. Loosen the screw in the oil test fitting (fig. 30) and allow as light seepage of oil to escape, then re-tighten the screw for a moment.
3. Crack open slightly the oil test fitting screw again.
   • If a steady flow of oil is evident, the oil level is either at or above the safe minimum level of 4 ounces, and no additional oil is required.
   • If no oil escapes or a hissing of escaping vapor only is detected, it is an indication that the oil is below the safe minimum level and oil should be added to the compressor.

Adding Oil

Before proceeding with this operation, the system should be checked for leaks and any leaks repaired prior to evacuating and recharging the system.

1. Purge and remove compressor from vehicle as described under "Compressor Replacement" in this section. To perform this operation it is not necessary to purge the entire system. Place compressor on a bench.
2. Position a clean container to catch oil drained from compressor, then remove oil test fitting screw and gasket and drain all oil from inside compressor.
3. Examine the oil for contaminants and measure the volume of drained oil to determine if compressor has been operating at less than the 4 ounces safe minimum quantity of oil. These conditions, together with the performance test and diagnosis, may be used to determine the extent of servicing required on the system. NOTE: If examination of the oil shows any foreign material, sludge, water, etc., further cleaning and processing of the system will be necessary. If an excessive amount of water is found, install a new receiver-dehydrator in the system. Flushing components with liquid Freon-12, obtained by turning the drum or can upside down, can be used to remove contaminants.
4. If the condition of the oil indicates that the compressor is free of any contamination, position the compressor so that the oil test elbow flange is on the top side and pour from the graduated bottle 9 ounces of new Frigidaire 525 viscosity oil into the compressor. CAUTION: Never use oil removed from compressor or system. Always use now oil!
5. Replace the oil test fitting gasket and screw.
6. Install compressor, tension drive belt on vehicle and evacuate the compressor and return system to normal operation as described under "Compressor Replacement."
7. Check system for proper operation, remove gauge lines and install gauge fitting caps and air cleaner.

The procedure outlined below is to be used when a diagnosis indicates either air or excessive refrigerant in the system. When a higher than normal high side operating pressure is encountered (see "Service Diagnosis"), then proceed as follows to purge and recharge the system.

1. With engine off and compressor hand shutoff valves in normal operating position (fully counterclockwise), remove air cleaner and connect high and low pressure gauge lines to gauge outlets on compressor, making sure gauge valves are closed.
2. Turn both compressor hand shutoff valves 1/4 turn clockwise.
3. Leak test the entire system. Repair any leaks detected.
4. With end of center gauge hose open, proceed to open high pressure gauge valve and allow vapor to exhaust slowly through the center gauge hose. When high pressure gauge indicates less then 100 lbs., open low pressure gauge valve and continue exhausting until all refrigerant has been purged from the system. CAUTION: Cover the connection with a cloth to prevent oil and refrigerant splashing about.
5. Complete gauge set hookup and evacuate the system as described under "Evacuating the System" in this section.
6. Add a complete charge of refrigerant as described under "Adding Refrigerant Complete Charge."
7. Operate the engine at 1500 RPM and check high side pressure and sight glass. When satisfied with operation of system, return compressor hand shutoff valves to normal operating position (fully counterclockwise), disconnect gauge set, remove jumper wire and replace valve caps and air cleaner.

Expansion Valve
Replacement of Valve Assembly

Expansion Valve

The thermostatic expansion valve is factory adjusted and preset and cannot be adjusted after installation. A malfunctioning valve must be replaced.

NOTE: Make sure all other possible causes of trouble have been checked before replacing valve. Also make sure power element bulb is properly positioned and tightly clamped to the evaporator.

Replacement of Valve Assembly

After attempting adjustment of the expansion valve, but before replacing the valve, make certain the liquid inlet screen is not clogged (see Figure 15). This operation may be performed after the conditioning unit has been removed and the expansion valve side of the unit housing disassembled (fig. 31). as described below. After checking the screen and the location and mounting of the thermobulb, proceed with replacement of the valve assembly. A malfunctioning valve may result from a stuck open or shut needle caused by corrosion or a discharged power element caused by a broken capillary line or tip.

1. Purge the system and remove the evaporator unit from the vehicle as described under "Evaporator Unit" in this section.
2. Remove the four clamps from the mating flanges of the two sections of the unit housing and remove the evaporator and expansion valve from the housing.
3. Remove the expansion valve power element bulb from low pressure line.
4. Remove the low pressure, and high pressure line flares in that order at the valve. Remove the valve.
5. Install the new valve by connecting the lines and clamp the power element of the new valve to the top of the low pressure line.
6. Assemble the housing to the evaporator and expansion valve and clamp the two sides of the housing together.
7. Install the evaporator unit to the vehicle as described under "Evaporator Unit."
8. Evacuate the system and check for leaks (see "Evacuating the System" in this section).
9. Charge the system with a complete charge (see "Adding Refrigerant" in this section). NOTE: Both compressor hand shutoff valves must be fully counterclockwise.
10. Check the system for proper operation.

Since the receiver-dehydrator and the sight glass are both in the high pressure liquid line, the procedure for replacing the sight glass will be basically the same as for replacing the receiver dehydrator. Refer to "Receiver-Dehydrator Replacement" described below for processing the system before and after removal of the sight glass.

Receiver-Dehydrator Replacement

The receiver-dehydrator should be replaced if it has been damaged through an accident or if it leaks or becomes restricted or clogged. Do not attempt to repair the receiver-dehydrator.

If at any time when examining the compressor oil, moisture is found or there is an indication of moisture at the expansion valve needle, the receiver-dehydrator should be replaced as follows:

1. Purge the system of refrigerant (see "Purging the System" in this section).
2. Disconnect the high pressure inlet line flare "A" at the receiver (fig. 32).
3. Disconnect the high pressure line and sight glass from the outlet on the receiver at "B."
4. Remove the receiver-dehydrator mounting bolts "C" and remove the unit.
5. Install the new receiver-dehydrator and connect high pressure lines at inlet and outlet of receiver. NOTE. Do not uncap the new receiver dehydrator until the last instant prior to installation as it will quickly pick up moisture from the air and ruin its efficiency in the system.
6. Evacuate the entire system (see "Evacuating the System" in this section).
7. Charge the system with a complete charge (see "Adding Refrigerant" in this section).

If the condenser becomes damaged through accident or collision, or develops a leak, it should be replaced as follows:

1. Purge the system and remove the receiver dehydrator from the system (see "'Receiver dehydrator Replacement-Steps 1-4 above). NOTE: If the original receiver-dehydrator is to be reused, it should be capped at the inlet and outlet connections immediately upon removal from the system.
2. Disconnect the high pressure inlet "D" at the top of the condenser (fig. 32). NOTE: If the new condenser is not to be installed immediately, be sure to plug the liquid line and the high pressure line connections.
3. Remove right and left horn bracket mounting bolts and remove horn and bracket assemblies from area of condenser.
4. Remove condenser mounting bolts and remove condenser.
5. Position a new condenser in front of radiator and install mounting bolts and horn and bracket assemblies.
6. Install the receiver-dehydrator, evacuate and charge the system (see "Receiver-Dehydrator Replacement" above).

If the flexible lines become damaged through accident or collision, or develop leaks, they should be replaced. Use only sealed lines from parts stock as replacement lines.

1. Purge the system of refrigerant (see "Purging the System" in this section).
2. Remove the line to be replaced by disconnecting it at the couplings and replace with a new line. NOTE: If for any reason new lines cannot be immediately replaced, cap or plug all open connections in the system.
3. Evacuate the system (see "Evacuating the System" in this section).
4. Charge the system (see "Adding Refrigerant" in this section).

Removal
Installation
Evaporator Replacement

Removal

1. Purge the system of refrigerant (see "Purging the System" in this section).
2. Remove air cleaner and battery from engine compartment. If desired, remove refrigerant line retainer on top of radiator support, loosen compressor brace and support pivot bolt, detach belt and swing compressor away from evaporator unit to obtain more clearance. Tighten pivot bolt to hold in this position.
3. Disconnect the high pressure liquid line connection to evaporator unit at front of unit and cap open ends.
4. Disconnect the low pressure line coupling at the evaporator unit and plug the line.
5. Remove three screws attaching unit to fender flange bracket and two bolts and reinforcement beneath the fender attaching the unit to the fender skirt. Disconnect wiring at the blower motor.
6. Remove four screws attaching transition to heater core housing and slide up two sliding cams to release transition and heater core assembly from core housing.

1. Attach heater core to transition with four screws. Lower the conditioning unit into position, engaging the four studs on the core housing into the four slots in the adapter. Slide cams down.
2. Connect the low pressure line coupling and the high pressure liquid line to the conditioning unit.
3. Evacuate the system (see "Evacuating the System" in this section).
4. Charge the system (see "Adding Refrigerant" in this section).
5. Install battery and air cleaner, reposition compressor and tension compressor belt. Install retainer to top of radiator support if removed.
6. Test for leaks and check operation of system.

The evaporator coil is located in the conditioning unit. If a leak develops in any of the tubes or soldered joints or if one becomes damaged, the assembly should be replaced. Do not attempt repairs of this unit.

If the evaporator is being replaced due to a refrigerant leak, first check to make sure that the leak is not coming from one of the flares or threaded fittings at the expansion valve before changing coils.

1. Remove the evaporator unit from the engine compartment as described under "Conditioning Unit".
2. Remove the four clamps, one to each side, which clamp together the two sides of the conditioning unit housing.
3. Separate the two sides of the housing and remove the evaporator coil being careful not to make any sharp kinks or bends in the thermostatic switch capillary tube. Remove this capillary tube from the evaporator.
4. Remove the expansion valve thermobulb from the line and remove the expansion valve from the coil. (See Expansion Valve Replacement.)
5. Install the expansion valve and thermobulb on new evaporator coil.
6. Leak test all connections, flares and the cooling coil. This can be done by using a 3/8" x 1/4" male flare connector in the liquid connections of the cooling coil. Attach a Freon 12 cylinder to this connector. Crack open the cylinder valve and allow Freon vapor to pass through the coil and out the suction line connection of the coil. While vapor is still escaping, cap the suction line connection. Allow the escaped vapor to dissipate into the air and then leak test. After a satisfactory leak test has been made close the cylinder valve, disconnect the cylinder and remove the cap and union fitting.
7. Attach the thermostatic switch capillary tube to the evaporator coil, install the coil in the housing and clamp the two sides of the housing together with the attaching clamps.
8. Install the unit in the vehicle as described under "Conditioning Unit-Installation." Also see fig. 33.
9. Test the operation of the system.

Replacement
Removal
Installation

Replacement

A malfunctioning compressor is one that will not turn over, has stuck crankshaft or pistons, burnt bearings, broken discharge or suction reeds or some internal difficulty which prevents the compressor from operating properly.

When such a difficulty is encountered, the compressor should be removed and a new compressor installed.

A new service compressor does not include clutch actuating coil parts, clutch pulley parts, or the suction and discharge connector. A service shipping plate is bolted over two "O" rings to seal the valve port openings. The two "O" rings under the shipping plate should be transferred to the old assembly and two new "O" rings used when installing the compressor on the car. A new compressor is charged with nine ounces of Frigidaire 525 Viscosity Oil, and a mixture of Freon-12 and nitrogen under approximately 40 psi pressure. An envelope attached to the compressor contains necessary shims for the air gap adjustment between the clutch plate armature and the coil housing.

Since the service compressor will be received less clutch actuating coil, clutch pulley and suction and discharge connector assembly, these components will normally be removed from the malfunctioning compressor and reinstalled on the new compressor.

The following procedure describes the complete removal, disassembly, assembly and installation operations for replacing a malfunctioning compressor. Refer to figures 34 and figure 35.

Removal

1. With engine off, remove air cleaner, connect high and low pressure gauge lines with adapters to the respective connections on the compressor (see "Installing Gauge Set to Check System Operation" in this section). Gauge valves should be closed to center connection. Compressor hand shutoff valves must be in full counterclockwise position.
2. Turn both compressor shutoff valves 3/4 turn clockwise.
3. Note high and low side gauges to determine that a pressure exists in both sides of the system. If a vacuum is observed, it will be necessary to break this by opening the two gauge valves. The center gauge connection must be capped while this is being done.
4. Close both compressor hand shutoff valves by turning fully clockwise.
5. Check both high and low pressure gauges. If pressure reads higher than 5 pounds, perform steps 6 and 7.
6. Remove plug from end of flexible line attached to center of gauge manifold and wrap end of line in rags to prevent splashing of oil or refrigerant.
7. Open high pressure gauge valve slowly and allow pressure to be reduced to 1 or 2 pounds on both gauges. Close gauge valves. Observe gauges and if pressure does not build up in excess of 5 pounds within 3 minutes proceed with step
8. If pressure is still in excess of 5 pounds, reopen high side gauge valve and allow pressure to reduce until it will not build up over 5 pounds. Back off the compressor connector attaching bolt just enough to loosen suction discharge connector and allow pressure inside to escape (fig. 35). Remove bolt and connectors after low side has been purged.
9. Disconnect electrical lead to clutch actuating coil. Remove gauge set and replace caps. Remove the two refrigerant line retainer to radiator support screws and remove retainer
10. Loosen brace and bracket pivot bolts and detach belt. Remove brace bolt and swing compressor to highest position. Retighten pivot bolt.
11. Remove the four bolts retaining compressor to mounting brackets, remove compressor assembly and place on a clean bench.
12. Since the service compressor will be received