A/C Compressor Relay Control

HVAC control module outputs A/C switch ON signal to ECM via BCM when the vehicle state satisfy conditions described below.

• A/C switch is ON
• Evaporator temperature is higher than specified value
• Evaporator temperature sensor malfunction is not detected

Communication of ECM and BCM is established by CAN (Controller Area Network). For more detail of CAN communication, refer to CAN COMMUNICATION SYSTEM DESCRIPTION .

ECM turns ON the A/C compressor relay when the vehicle state satisfy conditions described below.

• A/C switch ON signal is input
• A/C refrigerant pressure is within specified range
• Engine speed is within specified range
• Engine coolant temperature is lower than specified value
• Throttle opening is lower than specified value
• Vehicle is not in either state of starting or quick acceleration
• ECT sensor malfunction is not detected
• A/C refrigerant pressure sensor malfunction is not detected
• Ignition switch is turned on and defrost switch is turned on.
• Ignition switch is turned on and defrost "MODE" (air flow) switch is selected to "D/F" mode.