Control Module HVAC: Description and Operation

Circuit Description

A/C control
When the ignition switch is ON and the blower switch is in any position except OFF the blower relay coil energizes and battery voltage is applied to the NC switch through the closed contact of the blower relay and fuse 9. With the A/C switch ON, the engine control module (ECM) will ground the coil of the A/C control relay after a short delay to adjust idle speed. Battery voltage will then be applied to the compressor magnetic clutch from the NC fuse through the closed contacts of the A/C relay. The A/C compressor then runs.