Air Conditioning Switch: Description and Operation

FUNCTION

The air conditioning system uses an Air Conditioning Control Module (ACM) for Engine Controller input. Select/predict signals from the ACM allow the Engine Controller to adjust idle speed for smoother operation.

The ACM also controls the operation of the compressor clutch.


OPERATION

When the operator makes an air conditioning selection, the ACM sends a select signal to the Engine Controller.

The ACM will then send a predict signal to the Engine Controller approximately 0.5 seconds before clutch activation. This allows the Engine Controller 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 Engine Controller stops, the ACM waits approximately 0.5 seconds, allowing the Engine Controller to drop the idle speed. After the delay, the compressor clutch is de-energized.