Air Conditioning
AIR CONDITIONINGThe refrigerant system components include the following:
- A/C compressor and clutch assembly
- A/C condenser core
- A/C evaporator core
- Receiver/drier desiccant bag
- 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, which relays the request to the PCM. An evaporator temperature sensor is used to cycle the A/C compressor off when the evaporator core temperature falls below an acceptable temperature.
The HVAC module will send an A/C request signal to the instrument cluster if the following conditions are met:
- A mode which requires A/C operation has been manually selected by the driver or automatically selected by the HVAC module in AUTO mode.
- The A/C evaporator temperature sensor is reading an acceptable evaporator core temperature.
When an A/C request is received, the A/C compressor clutch will only be engaged by the PCM through the A/C clutch relay if all of the following conditions are met:
- The engine has been running for more than 5 seconds.
- Engine speed is above 425 rpm and below 5,800 rpm.
- The A/C pressure transducer is reading an acceptable pressure in the high side of the refrigerant system.
- 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: A/C compressor components are not serviced separately. The A/C compressor is serviced only as an assembly.
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 the oil matching procedure specified for this vehicle when installing a new A/C compressor.
When battery voltage is applied to the A/C compressor clutch field coil, the clutch disc 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 Condenser
NOTE: The A/C condenser for this vehicle is produced from the factory with a receiver/drier desiccant bag installed in the integrated receiver/drier. This receiver/drier desiccant bag may become contaminated with moisture if the A/C condenser is not installed for an extended period of time. Since it cannot be determined how much time has elapsed between production and installation of the unit as a service part, the receiver/drier desiccant bag must be removed and replaced with the separate receiver/drier desiccant bag, which is supplied together with the A/C condenser service part kit.
The A/C condenser 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 A/C condenser. The receiver/drier desiccant bag is a separate component and can be separately removed and installed with the A/C condenser removed from the vehicle.
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 liquid 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. During A/C compressor operation, airflow 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 at the evaporator core inlet and outlet tubes at the center 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.
Receiver/Drier
NOTE: Installation of a new receiver/drier desiccant bag 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 desiccant bag. Damage to the receiver/drier desiccant bag includes physical damage to the receiver/drier desiccant bag 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 system before repairs are carried out, the receiver/drier desiccant bag should not be replaced.
The receiver/drier is integral to the A/C condenser. It stores high-pressure liquid refrigerant after it leaves the condenser core. A receiver/drier desiccant bag installed inside the receiver/drier removes any retained moisture from the refrigerant. The receiver/drier desiccant bag is a separate component and can be separately removed and installed with the A/C condenser removed from the vehicle.
Evaporator Temperature Sensor
The evaporator temperature sensor contains a thermistor which receives a reference voltage from the HVAC module. The thermistor then varies the resistance to the reference voltage based on the evaporator fin temperature. The resulting voltage is returned to the HVAC module where it is interpreted as an evaporator fin temperature reading.
The HVAC module maintains evaporator core temperature and prevents icing of the evaporator core. It does this by switching off the A/C request signal to the instrument cluster when the evaporator temperature sensor reading falls below acceptable levels, and by switching on the A/C request when the evaporator temperature rises above acceptable levels.
The evaporator temperature sensor electrical connector is located outside of the heater core and evaporator core housing near the accelerator pedal, 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 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. It is not necessary to recover the refrigerant before removing the A/C pressure transducer.
Service Gauge Port Valves
The high-pressure service gauge port valve is located on the compressor-to-condenser discharge line.
The low-pressure service gauge port valve is located on the compressor suction line.
The fitting is an integral part of the refrigerant 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
A fluorescent refrigerant system dye "wafer" is added to the receiver/drier desiccant bag to assist in refrigerant system leak diagnosis using a Rotunda-approved ultraviolet blacklight. This fluorescent dye "wafer" will dissolve after about 30 minutes of continued A/C operation. 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, etc.