Air Conditioning
Air Conditioning
The refrigerant system components include the following:
- A/C compressor and clutch assembly
- A/C condenser core
- A/C evaporator core
- Receiver/drier
- Connecting refrigerant lines
- Thermostatic Expansion Valve (TXV)
The A/C compressor contains a pressure relief valve to protect the refrigerant system against excessively high refrigerant pressures.
A/C Compressor and Clutch Assembly
NOTE: Internal A/C compressor components are not serviced separately. The A/C compressor is serviced as an assembly. A new A/C pressure relief valve is included with replacement A/C compressors, but the valve is also available as a separate component and can be independently replaced if needed. The A/C compressor clutch, A/C compressor pulley and A/C clutch field coil can be serviced separately.
The A/C compressor has the following characteristics:
- A non-serviceable shaft seal.
- Uses PAG Refrigerant Compressor Oil (R-134a Systems) YN-12-D. This oil contains special additives required for the A/C compressor.
- The A/C compressor oil may darken over time while maintaining normal oil viscosity. This is normal because of break-in wear.
- Use the refrigerant oil adding procedure specified for this vehicle when installing a new A/C compressor or any other A/C component.
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 compressor pulley. The magnetic force locks the clutch disc and hub assembly and the A/C compressor pulley together as one unit, causing the compressor shaft to rotate with the engine. When battery voltage is removed from the A/C compressor clutch field coil, springs in the clutch disc and hub assembly move the clutch disc away from the A/C compressor 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 leaking around the threads, install a new A/C pressure relief valve and O-ring. If the new A/C pressure relief valve still vents after it is installed, 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 can be serviced separately from the A/C compressor. It is necessary to recover the refrigerant before removing the A/C pressure relief valve.
A/C Condenser Core
The condenser core 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 condenses gas to liquid refrigerant as it is cooled.
A/C 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, air flow 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 (Thermostatic Expansion Valve) 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 (Thermostatic Expansion Valve) 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 is not required when repairing the A/C system, unless there is physical evidence of contamination from a failed A/C compressor or damage to the receiver/drier. Damage to the receiver/drier includes leaks, physical damage to the receiver/drier shell or desiccant, 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, a new receiver/drier should not be installed.
The receiver/drier is mounted to the RH side of the condenser core above the condenser outlet fitting. It stores high-pressure liquid after it leaves the condenser core. A desiccant cartridge mounted inside the receiver/drier removes moisture from the refrigerant.
Evaporator Discharge Air Temperature Sensor
The evaporator discharge air temperature sensor contains a thermistor. The resistance of this thermistor varies by a specific amount based on the evaporator discharge air temperature. The PCM measures a voltage ratio between the reference voltage it supplies to the sensor and the sensor voltage to determine this resistance and the associated evaporator discharge air temperature.
As the evaporator core removes heat and moisture from the air flow moving through the evaporator core fins, the removed moisture condensates on the exterior of the evaporator core. The PCM uses input from the evaporator discharge air temperature sensor to prevent this moisture from freezing on the exterior of the evaporator core, and inhibiting air flow through the evaporator core fins. When the evaporator core temperature drops to a temperature near the freezing point of water, the PCM switches off the A/C compressor. The A/C compressor is switched back on when the evaporator core temperature rises to an acceptable level.
The evaporator discharge air temperature sensor is located below the glove compartment outside of the heater core and evaporator core housing.
A/C Pressure Transducer
The A/C pressure transducer monitors the compressor discharge pressure and communicates with the PCM. The PCM interrupts A/C compressor operation in the event the A/C pressure transducer indicates high system discharge pressures. It also to senses 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.
The A/C pressure transducer is located at the lower RH corner of the condenser core near the condenser outlet fitting. 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 near the condenser inlet fitting.
The low-pressure service gauge port valve is located on the A/C compressor suction line near the RH shock tower.
The service gauge port valve is an integral part of the refrigerant system line or component.
- Special couplings are required for both the high-side and low-side service gauge ports.
- A very small amount of leakage is always detectable around the Schrader-type valve with the service gauge port valve cap removed, and is considered normal. If the seal leaks excessively, install a new Schrader-type valve core.
- The service gauge port valve caps each include an O-ring seal used as a primary seal in the refrigerant system to prevent any leakage through the Schrader-type valves from reaching the atmosphere. Check the service gauge port valve cap O-ring seals when checking the refrigerant system for leaks and install a new cap if necessary. 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 when using a Rotunda-approved ultraviolet black light. 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. Replacement receiver/driers are shipped with a fluorescent dye "wafer" included in the desiccant bag, which dissolves after approximately 30 minutes of continued A/C operation. It is not necessary to add dye after flushing or filtering the refrigerant system because a new receiver/drier is installed as part of the flushing or filtering procedure. Only add additional refrigerant system dye if more than 50% of the refrigerant system lubricant capacity has been lost due to a fitting separation or hose rupture.