Control Module HVAC: Description and Operation

The air conditioner amplifier inputs the ECM through terminals A/C and ACT.

The ECM uses the A/C terminal signal to control idle speed during air conditioning operation. The ECM uses the ACT terminal signal to cut air conditioning operation during vehicle acceleration in order to increase performance. The air conditioning magnetic switch is turned off for several seconds under the following conditions:

During acceleration at speeds of 16 mph or less
Engine speed of 1600 rpm or less
Throttle valve opening angle at 60° or more