Air Conditioner Switch & Power Relay: Operation

• The air conditioner switch applies battery voltage to the engine control unit when the air conditioner is switched on.
• When the air conditioner signals are input, the engine control unit activates the idle speed control servo, 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 conditioner compressor's magnetic clutch is activated. See Fig 1 .

Fig 1: Identifying Air Conditioner Switch & Power Relay Circuit

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.