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 by CAN communication system. For more information about CAN communication system, refer to Description and Operation 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

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.