A/C Signal: Description and Operation
PURPOSE/OPERATIONThe air conditioning switch applies battery voltage to the engine control module when the air conditioning is switched ON.
When the air conditioning signals are input, the engine control module activates the idle-speed control motor, and also switches ON the power transistor. As a result, current flows to the power relay coil and the relay switch is switched ON; the air conditioning compressor's magnetic clutch is activated.