A/C Switch

A/C System Circuit Diagram (C67 A/C W/Out Climate Control):

The A/C switch applies battery voltage to the A/C request terminal of the ECM/PCM. The ECM/PCM then turns the A/C clutch relay "ON" and modifies the signal to the idle air control valve to increase the idle speed. Increasing the idle speed is necessary to compensate for the added load on the engine and to ensure efficient operation of the A/C system.