The compressor combines with the thermal expansion valve on the evaporator to form a largely self-regulating system. In the high-pressure refrigerant line, there is a pressure sensor rather than a traditional high- or low-pressure cutoff switch, or pressure cycling switch. The compressor clutch is controlled by the powertrain control module (PCM), or the engine control module (ECM), which monitors data from various engine systems. The PCM, or ECM, will disengage the compressor clutch if the following conditions are detected:

The compressor clutch will remain disengaged until normal operation is established.

All compressors are belt-driven from the engine crankshaft through the compressor clutch pulley. The compressor pulley rotates without driving the compressor shaft until an electromagnetic clutch coil is energized. When voltage is applied to energize the clutch coil, the clutch plate and hub assembly are drawn toward the pulley. The magnetic force locks the clutch plate and the pulley together as one unit to drive the compressor shaft.

As the compressor shaft is driven, it compresses the lowpressure refrigerant vapor from the evaporator into a high-pressure, high-temperature vapor. The refrigerant oil which is used to lubricate the compressor is carried with the refrigerant.

Refer to "V5 Air Conditioning Compressor Overhaul" in this section for complete overhaul procedure.

The condenser assembly in front of the radiator consists of coils which carry the refrigerant and cooling fins that provide the rapid transfer of heat. The air passing through the condenser cools the high-pressure refrigerant vapor and causes it to condense into a liquid.

The expansion valve is located on the passenger compartment side of the dash panel, near the right front strut tower.

The expansion valve can fail in three different positions: open, closed, or restricted.

An expansion valve that fails in the open position will result in a noisy A/C compressor or no cooling. The cause can be a broken spring, a broken ball, or excessive moisture in the A/C system. If the spring or the ball are found to be defective, replace the expansion valve. If excessive moisture is found in the A/C system, recycle the refrigerant.

An expansion valve that fails in the closed position will result in low suction pressure and no cooling. This may be caused by a failed power dome or excessive moisture in the A/C system. If the power dome on the expansion valve is found to be defective, replace the expansion valve. If excessive moisture is found in the A/C system, recycle the refrigerant.

A restricted expansion valve will result in low suction pressure and no cooling. This may be caused by debris in the refrigerant system. If debris is believed to be the cause, recycle the refrigerant, replace the expansion valve, and replace the receiver-dryer.

The evaporator is a device which cools and dehumidifies the air before it enters the vehicle. High-pressure liquid refrigerant flows through the expansion tube (orifice) and becomes a low-pressure gas in the evaporator. The heat in the air passing through the evaporator core is transferred to the cooler surface of the core, which cools the air. As the process of heat transfer from the air to the evaporator core surface is taking place, any moisture in the air condenses on the outside surface of the evaporator core and is drained off as water.

It acts as a refrigerant storing container, receiving liquid and some vapor and refrigerant oil from the evaporator.

At the bottom of the receiver-dryer is the desiccant, which acts as a drying agent for the moisture that may have entered the system. An oil bleed hole is located near the bottom of the receiver-dryer outlet pipe to pro-vide an oil return path to the compressor. The receiver-dryer is serviceable only as an assembly with the condenser.

The heater core heats the air before it enters the vehicle. Engine coolant is circulated through the core to heat the outside air passing over the fins of the core. The core is functional at all times and may be used to temper conditioned air in the A/C mode as well as in the heat or the vent mode.

A thermistor is a sensor which detects the temperature of refrigerant in the evaporator. If the temperature of a evaporator drops to 0°C (32°F) or below, the evaporator core gets stuck with frost or ice, resulting in reduced airflow and impaired cooling capability.

To prevent this, the engine control module (ECM) monitors the temperature signal from the thermistor and control the operation of the compressor. If a temperature of the evaporator drops to 2°C (35.6°F), the compressor clutch is disengaged until the temperature goes over 4°C (39.2°F).

The thermistor is located in the evaporator.

The operation of the A/C system is controlled by the switches and the lever on the control head. The compressor clutch and the blower are connected electrically to the control head by a wiring harness. The blower circuit is open in the OFF mode. Airflow is provided by the four blower speeds available in the remaining modes. Cooled and dehumidified air is available in the MAX, NORMAL, BI-LEVEL, and DEFROST modes.

The temperature is controlled by the position of the temperature knob on the control head. A cable connects this knob to the temperature door, which controls the airflow through the heater core. As the temperature knob is moved through its range of travel, a sliding clip on the cable at the temperature valve connection should assume a position ensuring that the temperature door will seat in both extreme positions. The temperature door position is independent of the mode control switch. The temperature door on some models is controlled electrically, eliminating the need for the temperature cable.

The electric engine cooling fan on some vehicles is not part of the A/C control system; however, the fan is operational any time the A/C control is in the MAX, NORMAL, or BI-LEVEL modes. Some models provide for engine cooling fan operation when the controller is in the DEFROST mode. This added feature is part of the A/C controller function and is aimed at preventing excessive compressor head temperatures. It also allows the A/C system to function more efficiently. On some models, the engine cooling fan will be turned off during road speed conditions above 56 km/h (35 mph), when the airflow though the condenser coil is adequate for efficient cooling. The operation of the cooling fan is controlled by the powertrain control module (PCM), or the engine control module (ECM), through the cooling fan relay.

The pressure transducer incorporates the functions of the high-pressure and the low-pressure cutout switches along with the fan cycling switch. The pressure transducer is located in the high-side liquid refrigerant line near the right front strut tower and the air filter assembly.

During full throttle acceleration on vehicles equipped with multi-port injection (MPI), the throttle position sensor (TPS) sends a signal to the PCM or the ECM, which then controls the compressor clutch.

This relay on some vehicles controls the current to the entire A/C system and provides a short delay of A/C operation upon start-up.

Different vehicles with V5 or SP10 compressors may exhibit differences in mounting and installation, but overhaul procedures are similar.

Before removing the compressor or performing on-vehicle repairs, clean the compressor connections and the outside of the compressor.

The compressor has been removed from the vehicle unless otherwise indicated.

Clean tools and a clean work area are important for proper servicing. Keep dirt and foreign material from getting on or into the compressor parts. Parts that are to be reassembled should be cleaned with trichloroethane, naphtha, stoddard solvent, kerosene, or equivalent solvents. Dry the cleaned parts with clean dry air. Use only lint-free cloths to wipe the parts.

The V5 is a variable displacement compressor that can match the automotive air conditioning (A/C) demand under all conditions without cycling. The basic compressor mechanism is a variable angle wobble-plate with five axially oriented cylinders. The center of control of the compressor displacement is a bellows-actuated control valve located in the rear head of the compressor. The control valve senses compressor suction pressure.

The wobble-plate angle and the compressor displacement are controlled by the crankcase suction pressure differential. When the A/C capacity demand is high, the suction pressure will be above the control point. The valve will maintain a bleed from crankcase to suction. With no crankcase suction pressure differential, the compressor will have maximum displacement.

When the A/C capacity demand is lower and the suction pressure reaches the control point, the valve will bleed discharge gas into the crankcase and close off a passage from the crankcase to the suction plenum. The angle of the wobble-plate is controlled by a force balance on the five pistons. A slight elevation of the crankcase suction pressure differential creates total force on the pistons resulting in a movement about the wobbleplate pivot pin that reduces the plate angle.

The compressor has a unique lubrication system. The crankcase suction bleed is routed through the rotating wobble-plate for lubrication of the wobble-plate bearing. The rotation acts as an oil separator which removes some of the oil from the crankcase suction bleed, re-routing it to the crankcase where it can lubricate the compressor mechanism.

The SP-10 is a fixed 110-cc displacement swash plate compressor. It consists of five double-ended pistons reciprocated in 10 clyinder bores by the swash plate & shaft assembly. There are 10 hemispheric shoes connecting the pistons to the swash plate and shaft assembly. As the swash rotates, the shoes swivel. Thus the rotary motion of the swash plate is converted to the reciprocating motion of the pistons.