A/C Operation Description at ECM: Notes

ECM controls the A/C compressor relay and condenser cooling fan relay according to signals from HVAC control unit, A/C refrigerant pressure sensor, ECT sensor and evaporator temperature sensor. The A/C switch ON signal from HVAC control unit is transmitted to ECM through BCM by CAN communication system. For more information about CAN communication system, 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 from HVAC control unit
• A/C refrigerant pressure is within specified range
• Evaporator temperature 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