A/C Operation Description at ECM

A/C Operation Description at ECM

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. For 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 inputted 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

Condenser Cooling Fan Relay Control
ECM turn ON the condenser cooling fan relay at the same time when ECM turn ON the A/C compressor relay.