A/C Signal: Description and Operation

PURPOSE
The A/C signal is an input to the Powertrain Control Module (PCM) which informs it that a request for A/C operation has been made. The PCM then determines if all of the requirements for A/C operation have been met:
- The engine must be running.
- The engine must not be overheating.
- The engine must not be operating at wide open throttle.
If these conditions are met the PCM will increase idle speed and then energize the A/C relay.

OPERATION
With the A/C demand switch closed and the A/C clutch cyclic pressure switch shut, battery voltage will be placed on circuit ACCS (10), informing the PCM of an A/C request. A/C clutch operation will not occur until the PCM grounds circuit WAC (54).

RELATED DIAGNOSTIC TROUBLE CODES

DTC 539 - A/C request during self test procedure.

DTC 559 - A/C ON circuit failure.