Throttle Full Open Switch: Description and Operation

PURPOSE
The Wide Open Throttle Air Conditioning Cut-off (WAC) output is used by the PCM to disengage the A/C clutch when compressor operation is not desirable.

OPERATION
Under normal conditions, with the A/C Off, the PCM will ground the WAC output, which opens the normally closed WAC relay. When the A/C demand switch is turned On, and the A/C cycling switch and A/C Pressure Switch (ACPSW) high pressure contacts are closed, voltage is supplied to the WAC relay contacts and to the ACCS circuit. The voltage on the ACCS circuit indicates to the PCM that A/C is requested. The PCM will then verify that A/C clutch operation is desirable (example: engine not cranking or overheated, not at WOT, etc.).

If A/C clutch operation is desirable, the PCM will adjust idle speed as necessary and "unground" the WAC output, which closes the normally open WAC relay and allows voltage to be supplied to the A/C clutch.