A/C Signal: Description and Operation

PURPOSE
The air conditioning signal is used to inform the Engine Control Module (ECM) that a request for air conditioning has been made.

OPERATION
When the A/C switch is closed and evaporator temperature is warm enough, the ECM receives a ground signal, informing the ECM that the air conditioning has been turned on. The ECM then controls the compressor relay and adjusts idle speed to compensate for compressor load.