Air Conditioning

Description
The air conditioning system uses a compressor with variable displacement. This compressor is referred to as the V-5 type compressor. The V-5 compressor meets A/C requirements without cycling.


Operation
The A/C compressor operation is controlled by the Powertrain Control Module (PCM) for the following reasons:

^ Improved idle quality during compressor clutch engagement.

^ Improved wide open throttle performance (WOT).

^ Protects the A/C compressor from operation with incorrect refrigerant pressures.


The A/C clutch electrical system consists of the following components:

^ The A/C control head and/or the A/C programmer.

^ The A/C refrigerant pressure sensor.

^ The A/C compressor clutch.

^ The A/C compressor clutch relay.

^ The PCM.

When an A/C mode is selected at the A/C control head, the A/C programmer provides a 12 volt signal to the A/C request circuit. The PCM monitors the A/C request circuit and controls the A/C compressor relay based on the A/C request signal. This allows the PCM to increase the engine idle speed just prior to A/C clutch engagement for better idle quality. In addition, the PCM will command the cooling fans ON during A/C operation. The PCM also monitors the A/C refrigerant pressure sensor circuit. If the A/C refrigerant pressure is too high or low, the PCM will disable the A/C compressor relay.

The PCM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested unless one or more of the following conditions are present:

^ Throttle angle is greater than 96%.

^ A/C head pressure is greater than 440 psi (4.6 volts) or less than 35 psi (0.4 volt) as determined by the A/C refrigerant pressure sensor.

^ Ignition voltage is less than 10.5 volts.

^ Engine speed is greater than 4400 RPM for any amount of time.

^ Engine speed is greater than 3700 RPM for longer than 5 seconds.

^ ECT is greater than 124°C (255°F).

^ IAT is less than 5°C (41°F).

Any of the conditions described above will inhibit A/C compressor relay operation.


Diagnosis
DTC P0530, P0560, P1639, or P1654 can affect A/C operation. Refer to the DTC tables if any DTCs are set.

The PCM Controlled Air Conditioning Diagnosis table should be used for diagnosing the electrical portion of the A/C compressor clutch circuit if a DTC is not set. To diagnose the refrigerant portion of the HVAC system, refer to the Heater, Ventilation, and Air Conditioning (HVAC) section. A scan tool will be used in diagnosing the system. The scan tool has the ability to display the A/C request and refrigerant pressure inputs to the PCM. The scan tool can display when the PCM has commanded the A/C clutch ON. The scan tool also has the ability to override the A/C request signal and energize the A/C control relay.