Air Conditioning

Air Conditioning

The A/C system components are the following:

- A/C compressor
- A/C condenser core
- A/C evaporator core
- Receiver/drier cartridge
- Connecting refrigerant lines
- Thermostatic Expansion Valve (TXV)
- Evaporator temperature sensor
- A/C pressure transducer
- A/C compressor pressure relief valve

The refrigerant system incorporates an A/C compressor controlled by the PCM through an A/C clutch relay.

The A/C compressor clutch will only be engaged by the PCM if all of the following conditions are met:

- The HVAC module is set to a mode which provides an A/C request to the PCM.
- The evaporator temperature sensor is reading a temperature above 3°C (37°F).
- The A/C pressure transducer is not reading an excessively high or excessively low pressure in the refrigerant system.
- The A/C compressor relay is switched to the CLOSED position by the PCM.
- The Engine Coolant Temperature (ECT) is not excessively high.
- The PCM has not detected a Wide Open Throttle (WOT) condition.

Refer to Climate Control System - General Information and Diagnostics Testing and Inspection for operating specifications.

An A/C compressor pressure relief valve is installed in the A/C compressor to protect the refrigerant system against excessively high refrigerant pressure.

Refrigerant flow into the evaporator core is metered by a TXV.


A/C Compressor and Clutch Assembly

NOTE: Internal FS20 A/C compressor components are not serviced separately. The A/C compressor is serviced only as an assembly. The clutch disc and hub, A/C compressor pulley and bearing and clutch field coil are serviceable.

NOTE: Installation of a new receiver/drier cartridge is not required when repairing the A/C system except when there is physical evidence of system contamination from a failed A/C compressor or damage to the receiver/drier cartridge.

The FS20 A/C compressor uses the following:

- A non-serviceable shaft seal.
- A pressure relief valve installed in the rear of the compressor to protect the refrigerant system against excessively high refrigerant pressures.
- PAG oil or equivalent. This oil contains special additives required for the A/C compressor.
- PAG oil may have some slightly dark-colored streaks while maintaining normal oil viscosity. This is normal for this A/C compressor because of break-in wear that can discolor the oil.

Use standard oil matching procedures when installing new compressors.

A/C Compressor Clutch Assembly









The magnetic A/C clutch has the following characteristics:

- The A/C clutch drives the compressor shaft.
- When battery positive voltage (B+) is applied to the A/C clutch field coil, the clutch disc and hub assembly is drawn toward the A/C clutch pulley.
- The magnetic force locks the clutch disc and hub assembly and the A/C clutch pulley together as one unit, causing the compressor shaft to rotate.
- When B+ is removed from the A/C clutch field coil, springs in the clutch disc and hub assembly move the clutch disc away from the A/C clutch pulley.


A/C Pressure Relief Valve

NOTE: If the A/C compressor is operating within limits and the A/C pressure relief valve is venting, or if the A/C pressure relief valve is leaking around the threads, replace the A/C pressure relief valve and O-ring. If the A/C pressure relief valve still vents after it is replaced, diagnose the refrigerant system for a restriction.

An A/C pressure relief valve is incorporated in the A/C compressor to prevent damage to the A/C compressor and other system components by relieving unusually high system discharge pressure buildups. For specifications regarding operating pressure(s), refer to Climate Control System - General Information and Diagnostics Climate Control System.

The A/C pressure relief valve is a separate component and can be replaced separately from the A/C compressor. It is necessary to recover the refrigerant before removing the A/C pressure relief valve.


Thermostatic Expansion Valve (TXV)

The TXV is located between the evaporator core lines and the TXV manifold and tube assembly at the RH rear of the engine compartment. The TXV provides a restriction to the flow of refrigerant from the high-pressure side of the refrigerant system, and separates the low-pressure and high-pressure sides of the refrigerant system. Refrigerant entering and exiting the evaporator core passes through the TXV through 2 separate flow paths. An internal temperature sensing bulb senses the temperature of the refrigerant flowing out of the evaporator core and adjusts an internal pin-type valve to meter the refrigerant flow into the evaporator core. The internal pin-type valve decreases the amount of refrigerant entering the evaporator core at lower temperatures and increases the amount of refrigerant entering the evaporator core at higher temperatures.


Evaporator Temperature Sensor

The evaporator temperature sensor communicates the evaporator fin temperature to the HVAC module.

The PCM maintains evaporator core temperature and prevents icing of the evaporator core, by disengaging the A/C compressor clutch when the evaporator temperature sensor reading falls below acceptable levels, and by engaging the A/C compressor clutch when the discharge air temperature rises above acceptable levels.

The evaporator temperature sensor electrical connector is located outside of the heater core and evaporator core housing behind the glove compartment, with the sensor pigtail leading into the housing to the sensor probe which is inserted between the evaporator core fins.

The evaporator temperature sensor is not available as a separate component. To install a new evaporator temperature sensor, a new heater core and evaporator core housing must be installed.


A/C Pressure Transducer

The A/C pressure transducer communicates the compressor discharge pressure to the PCM. The PCM will interrupt A/C compressor operation in the event that the A/C pressure transducer indicates excessively high system discharge pressures. It is also used to sense low charge conditions. If the pressure is below a predetermined value for a given ambient temperature, the PCM will not allow the clutch to engage.


A/C Condenser/Power Steering Combo Cooler

The A/C condenser/power steering combo cooler is an aluminum fin-and-tube design heat exchanger located in front of the vehicle radiator. It cools compressed refrigerant gas by allowing air to pass over fins and tubes to extract heat and by condensing gas to liquid refrigerant as it is cooled.

The receiver/drier is incorporated onto the LH side of the condenser core. The receiver/drier cartridge is a separate component and can be removed and installed separately from the condenser core.

The top portion of the condenser/power steering combo cooler is partitioned from the refrigerant system and is used for power steering fluid cooling.


Evaporator Core

NOTE: If an evaporator core leak is suspected, the evaporator core must be vacuum leak tested before it is removed from the vehicle. Refer to Climate Control System - General Information and Diagnostics Testing and Inspection.

The evaporator core is an aluminum plate/fin type and is located in the heater core and evaporator core housing. A mixture of liquid refrigerant and oil enters the bottom of the evaporator core through the evaporator core inlet tube, continues over to the plate/fin sections and then moves out of the evaporator core through the evaporator core outlet tube as a vapor. Airflow from the blower motor is cooled and dehumidified as it flows through the evaporator core fins.


Receiver/Drier

NOTE: Installation of a new receiver/drier cartridge is not required when repairing the A/C system, except when there is physical evidence of contamination from a failed A/C compressor or damage to the receiver/drier cartridge. Damage to the receiver/drier cartridge includes physical damage or moisture contamination. Moisture contamination results only from a complete loss of refrigerant, and equalization of the refrigerant system pressure with atmospheric pressure for a period longer than one hour. If even a slight amount of positive refrigerant pressure is present in the refrigerant system before repairs are carried out, the receiver/drier cartridge does not need to be replaced.

The receiver/drier is integral to the A/C condenser/power steering combo cooler. It stores high-pressure liquid after it leaves the condenser core. An A/C desiccant cartridge mounted inside the receiver/drier removes any retained moisture from the refrigerant. The receiver/drier desiccant cartridge is a separate component and can be removed and installed separately from the A/C condenser/power steering combo cooler.


Service Gauge Port Valves

The high-pressure service gauge port valve is located on the high-pressure side of the TXV manifold and tube at the RH rear of the engine compartment.

The low-pressure service gauge port valve is located on the low-pressure side of the TXV manifold and tube at the RH rear of the engine compartment.











The fitting is an integral part of the refrigeration line or component.

- Special couplings are required for both the high-side and low-side service gauge ports.
- A very small amount of leakage will always be detectable around the Schrader-type valve, with the service gauge port valve cap removed, and is considered normal. A new Schrader-type valve core can be installed if the seal leaks excessively.
- The service gauge port valve caps are used as primary seals in the refrigerant system to prevent leakage through the Schrader-type valves from reaching the atmosphere. Always install and tighten the A/C service gauge port valve caps to the correct torque after they are removed.


Refrigerant System Dye

Fluorescent refrigerant system dye is added to the refrigerant system at the factory to assist in refrigerant system leak diagnosis using a Rotunda-approved ultraviolet blacklight. It is not necessary to add additional dye to the refrigerant system before diagnosing leaks, even if a significant amount of refrigerant has been removed from the system. Additional refrigerant system dye should only be added if more than 50% of the refrigerant system lubricant capacity has been lost due to a fitting separation, hose rupture or other damage. Refer to Climate Control System - General Information and Diagnostics Testing and Inspection.