Wide Open Throttle A/C Cut-Off

Wide Open Throttle A/C Cut-Off

Mustang

The Wide Open Throttle Air Conditioning Cut-off (WAC) output is used by the PCM to disengage the A/C clutch when A/C compressor operation is not desirable. Under normal conditions, with the A/C off, the PCM will ground the WAC output, which opens the normally closed WOT A/C cut-off relay inside the constant control relay module. When the A/C demand switch is turned on, and the A/C cycling switch and A/C high pressure switch high pressure contacts are closed, voltage is supplied to the WOT A/C cut-off 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 (for example, engine not cranking, overheated or not at WOT). If A/C clutch operation is desirable, the PCM will adjust idle speed as necessary and "unground" the WAC output. This closes the normally closed WOT A/C cut-off relay and allows voltage to be supplied to the A/C clutch.

All Others

For these applications, the wide open throttle A/C cutoff relay (may be referred to as the A/C clutch relay) is normally open. There is no direct electrical connection between the A/C switch or EATC Module and the A/C clutch. The PCM will receive a signal indicating that A/C is requested (for some applications, this message is sent through the BUS + and BUS - circuits). When A/C is requested, the PCM will check other A/C related inputs that are available (such as ACP (SW), ACCS). If these inputs indicate A/C operation is OK, and the engine conditions are OK (such as coolant temperature, engine rpm, throttle position), the PCM will ground the WAC output, closing the relay contacts and sending voltage to the A/C clutch.