Compressor Clutch Relay: Description and Operation

Air Conditioning Relay:

When the air conditioner switch is turned on, while the engine is at idle, the Idle Speed Control (ISC) servo operates to increase the engine speed and the ECU advances the ignition timing, to maintain ideal idle speed. However, there is some delay before the engine speed actually increases. To maintain the engine free from the air conditioner load during that delay period, the ECU keeps the power off for about 0.5 seconds to open the air conditioner power relay circuit. As a result, even if the air conditioner switch is on, the air compressor is not driven instantly, preventing engine speed drop due to compressor load. In addition, for automatic transmission equipped models, during acceleration when the throttle valve opening is above 65°, the air conditioner power relay circuit is shut off for approximately five seconds to enhance acceleration performance.