Circuit/System Description

When the A/C switch is pressed, the HVAC control module grounds the A/C request signal circuit. The body control module (BCM) receives the ground input and sends a GMLAN message to the engine control module (ECM) for an A/C request. This input will request the ECM to ground the A/C compressor clutch relay control circuit, which will switch the A/C CLUTCH relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch assembly.