Air Conditioning

The A/C system components include the following:

• A/C compressor and clutch assembly
• A/C condenser core
• A/C evaporator core
• Receiver/drier desiccant bag (3.5L Ti-VCT engine)
• Receiver/drier (3.5L GTDI engine)
• Connecting refrigerant lines
• TXV

A/C Compressor and Clutch Assembly

NOTE: The A/C compressor components are not serviced separately. The A/C compressor and clutch is serviced only as an assembly.

The A/C compressor has the following characteristics:

• A non-serviceable shaft seal.
• A non-serviceable pressure relief valve is installed in the rear of the A/C compressor to protect the refrigerant system against excessively high refrigerant pressures.
• Uses PAG oil or equivalent. This oil contains special additives required for the A/C compressor.
• The oil may have some slightly dark-colored streaks while maintaining normal lubricant properties. This is normal for this A/C compressor because of break-in wear that can discolor the oil.
• Use the refrigerant oil adding procedure specified for this vehicle when installing a new A/C compressor. Refer to Section 412-00 .

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 disc 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 disc and hub assembly move the clutch disc away from the A/C clutch pulley.

A/C Condenser/Transmission Oil Combo Cooler

NOTE: The A/C condenser/transmission oil combo cooler for the 3.5L Ti-VCT engine equipped vehicles 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, remove and replace the receiver/drier desiccant bag with the separate receiver/drier desiccant bag supplied with the A/C condenser service part kit.

The A/C condenser/transmission oil 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 top portion of the A/C condenser/transmission oil combo cooler is partitioned from the refrigerant system and is used for transmission oil cooling.

Receiver Drier

NOTE: It is not necessary to install a new receiver/drier 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. Damage to the receiver/drier includes leaks in the receiver/drier, 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 system before repairs are carried out, the receiver/drier should not be replaced.

The receiver/drier stores high-pressure liquid and the desiccant bag mounted inside the receiver/drier removes any retained moisture from the refrigerant.

For 3.5L Ti-VCT engine equipped vehicles, the receiver/drier is integral to the A/C condenser. The receiver/drier desiccant bag is a separate component and can be removed and installed with the A/C condenser in the vehicle.

For 3.5L GTDI engine equipped vehicles, the receiver/drier is mounted between the condenser outlet and the TXV manifold and tube assembly.

Evaporator Core

NOTE: The evaporator core is available only as part of the heater core and evaporator core housing.

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.

TXV

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

NOTE: 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.

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 interpreted as an evaporator fin temperature reading.

The HVAC module maintains evaporator core temperature and prevents the evaporator core from icing. This is accomplished by switching the A/C request signal off when the evaporator temperature sensor reading falls below acceptable levels, and by switching the A/C request signal on 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 inserted between the evaporator core fins.

A/C Pressure Transducer

The A/C pressure transducer monitors the compressor discharge pressure and sends a variable voltage signal representing the pressure to the PCM. The PCM interrupts A/C compressor operation in the event the A/C pressure transducer indicates high system discharge pressures. It is also used to sense low charge conditions. The PCM prevents the A/C clutch from engaging if the pressure is below a predetermined value for a given ambient temperature. 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 around the Schrader-type valve with the service gauge port valve cap removed is considered normal. Install a new Schrader-type valve core if the seal leaks excessively.
• The A/C 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 UV blacklight. This fluorescent dye wafer dissolves 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 or hose rupture. Refer to Section 412-00 .