Compressor HVAC: Description and Operation

CIRCUIT OPERATION
The A/C Compressor for the Air Conditioning System is belt-driven by the engine through the A/C Compressor Clutch. The clutch allows the compressor to be disengaged when air conditioning is not required, or to remove the air conditioning load from the engine when necessary.

Operation of the compressor depends on the particular A/C mode selected by the driver. When the A/C Mode Selector is in MAX, NORM, HI-LEVEL or DEF, battery voltage is applied through Fuse 8 and the Heater and A/C Control Assembly Selector to the A/C Compressor Control Relay.

DESCRIPTION
The A/C Compressor Control Relay is operated by the Electronic Control Module (ECM). When the ECM receives the A/C On signal (battery voltage) at terminal C1/C9, the ECM grounds terminal C3/F2, which energizes the relay. When the A/C Compressor Control Relay is energized, voltage is applied to the A/C Compressor Clutch through the contacts of the relay. If the ECM determines that the A/C load should be reduced, such as during full throttle, the ECM de-energizes the A/C Compressor Control Relay. This removes voltage from the A/C Compressor Clutch and removes the A/C load from the engine.