Compressor HVAC: Description and Operation

The Compressor for air conditioning is belt driven by the Engine. The A/C Compressor Clutch engages and disengages the Compressor to remove the air conditioning load from the Engine when needed. The A/C Compressor Control Clutch engages the Compressor when the A/C mode selector is in "MAX," "NORM", "BI-LEVEL," or "DEFROST."

The A/C Clutch Diode connected across the A/C Compressor Clutch suppresses high voltage spikes that are generated by the collapsing magnetic field of the clutch coil when the clutch is turned OFF.

The A/C Compressor Control Relay opens and closes the circuit to the A/C Compressor Clutch. The coil of the relay is grounded by the Powertrain Control Module (PCM). This enables the PCM to disengage the air conditioning to reduce the load on the Engine when required. Wide open throttle, high power steering pressure or coolant temperature will also prevent the A/C system from engaging.

The PCM receives an air conditioning "ON" signal, which is battery voltage from the Heater-A/C Control Assembly. It signals the PCM that A/C Compressor operation is required. The PCM also monitors a signal voltage from the A/C Pressure Sensor. If either a low or high refrigerant pressure condition occurs, the PCM will prevent the A/C Compressor Clutch from engaging.

Refer Powertrain Management (PCM) for complete operating details. Powertrain Management