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
When both the A/C demand switch and the low pressure cutout switch are shut circuit ACD (10) is grounded informing the PCM of an A/C request. If all conditions for A/C operation are met the PCM will energize the A/C relay by grounding circuit AC ON (54).


RELATED DIAGNOSTIC TROUBLE CODES

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

DTC 559 - A/C ON circuit failure.