Air Conditioning System: Manual Type 7B-3
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 in Section 1A".
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.