Early Models

The air conditioning system uses an Air Conditioning Control Module (ACM) to communicate with the Engine Control Unit (ECU). When the operator makes an air conditioning selection, the ACM sends a signal to the ECU so the ECU can compensate for the additional engine load.

The ACM controls the operation of the compressor clutch. The ACM will send a predict signal to the ECU approximately 0.5 seconds before clutch activation. This allows the ECU to increase the idle speed for the increase in engine load. The predict signal is sent continuously until the operator turns OFF the air conditioning compressor. When the signal to the ECU stops, the ACM waits approximately 0.5 seconds, allowing the ECU to drop the idle speed. After the delay, the compressor clutch is DE-ENERGIZED.