Air Conditioning
Air Conditioning
The refrigerant system components include the following:
- A/C compressor
- A/C clutch assembly
- A/C condenser core
- A/C evaporator core
- Receiver/drier cartridge
- Connecting refrigerant lines
- Thermostatic Expansion Valve (TXV)
The refrigerant system incorporates an A/C compressor controlled by the PCM through an A/C clutch relay. The HVAC module sends an A/C request signal to the Instrument Cluster (IC), which relays the request to the PCM. An evaporator discharge air temperature sensor is used to disengage the A/C compressor clutch when the evaporator core temperature falls below an acceptable temperature.
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 via the IC.
- The evaporator discharge air temperature sensor is reading an acceptable temperature.
- The A/C pressure transducer is reading an acceptable pressure in the high side of the refrigerant system.
- The A/C compressor relay is switched to the closed position by the PCM.
- The engine coolant temperature is not excessively high.
- The PCM has not detected a Wide Open Throttle (WOT) condition.
An A/C pressure relief valve is installed in the A/C compressor to protect the refrigerant system against excessively high refrigerant pressures.
Refrigerant flow into the evaporator core is metered by a TXV.
A/C Compressor and Clutch Assembly
NOTE: Internal 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.
The A/C compressor has the following characteristics:
- A non-serviceable shaft seal
- A pressure relief valve is installed in the rear of the compressor to protect the refrigerant system against excessively high refrigerant pressures
- The A/C compressor uses PAG oil or equivalent. This oil contains special additives required for the A/C compressor
- The A/C compressor 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
When battery voltage is applied to the A/C compressor clutch field coil, the clutch plate and hub assembly is drawn toward the A/C clutch pulley. The magnetic force locks the clutch plate and hub assembly and the A/C clutch pulley together as one unit, causing the compressor shaft to rotate. When battery voltage is removed from the A/C compressor clutch field coil, springs in the clutch plate and hub assembly move the clutch plate 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.
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.
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 (desiccant) 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.
Receiver/Drier Cartridge
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. A receiver/drier (desiccant) cartridge mounted inside the receiver/drier removes any retained moisture from the refrigerant. The receiver/drier cartridge is a separate component and can be removed and installed separately from the A/C condenser/power steering combo cooler.
Evaporator Core
The evaporator core is an aluminum plate/fin type and is located in the heater core and evaporator core housing. A mixture of refrigerant and oil enters the bottom of the evaporator core through the evaporator core inlet tube and continues out of the evaporator core through the evaporator core outlet tube as a vapor. Air from the blower motor is cooled and dehumidified as it flows through the evaporator core fins.
Thermostatic Expansion Valve (TXV)
The Thermostatic Expansion Valve (TXV) is located between the evaporator core lines and the TXV manifold and tube assembly at the 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 Discharge Air Temperature Sensor
The evaporator discharge air temperature sensor contains a thermistor which receives a reference voltage from the PCM. The thermistor then varies the resistance to the reference voltage based on the evaporator discharge air temperature. The resulting voltage is returned to the PCM where it is interpreted as an evaporator discharge air temperature reading.
The PCM maintains evaporator core temperature and prevents icing of the evaporator core, by disengaging the A/C compressor clutch when the evaporator discharge air 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 discharge air temperature sensor is located inside of the heater core and evaporator core housing in the air-stream leaving the evaporator core.
A/C Pressure Transducer
The A/C pressure transducer monitors the compressor discharge pressure and communicates with the PCM. The PCM will interrupt A/C compressor operation in the event that the A/C pressure transducer indicates 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.
Service Gauge Port Valves
The high-pressure service gauge port valve is located on the condenser-to-evaporator line.
The low-pressure service gauge port valve is located on the TXV manifold and tube assembly.
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 UV 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 or hose rupture.