A/C Operation Description (Diesel Model)
Precautions: General safety (00)
Upon receiving A/C switch ON signal from HVAC control unit, ECM controls A/C compressor relay and radiator (condenser) cooling fan relay as described in the table below.
The A/C switch ON signal from the HVAC control unit is transmitted to ECM through BCM. For CAN communication system, refer to Communication System Description:D16AA Model.
| Control item | Input sensor (or signal) | Description | |
|---|---|---|---|
| A/C compressor relay control | Evaporator temperature | Evaporator temperature sensor | ECM controls A/C compressor by turning A/C compressor relay ON/OFF according to request signal from BCM. BCM sends the signal based on the signal from evaporator temperature sensor to prevent evaporator from freezing. |
| Control during low engine speed | CKP sensor (engine rpm) | ECM stops A/C compressor by turning A/C compressor relay OFF according to signal from CKP sensor (engine rpm) to prevent engine from stalling while engine speed is low. | |
| Control at abnormal refrigerant pressure | A/C refrigerant pressure sensor |
•ECM stops A/C compressor by turning A/C compressor relay OFF according to signal from A/C refrigerant pressure sensor to protect system when refrigerant pressure is abnormal.
•ECM stops A/C compressor by turning A/C compressor relay OFF when A/C refrigerant pressure sensor malfunctions. |
|
| Control during acceleration | Accelerator pedal position sensor and wheel speed sensor |
•ECM stops A/C compressor temporarily by turning A/C compressor relay OFF according to signal from accelerator pedal position sensor to provide enough acceleration while accelerator pedal is fully depressed regardless of vehicle speed.
•ECM stops A/C compressor temporarily by turning A/C compressor relay OFF according to signal from throttle position sensor to provide enough acceleration when accelerator pedal is depressed more than specification while vehicle speed is low. |
|
| Control at high engine coolant temperature | ECT sensor |
•ECM stops A/C compressor by turning A/C compressor relay OFF according to signal from ECT sensor to prevent overheating when engine coolant temperature is higher than specified level.
•ECM stops A/C compressor by turning A/C compressor relay OFF when ECT sensor malfunctions. |
|
| Radiator (condenser) cooling fan relay control | A/C refrigerant pressure sensor | ECM drives radiator cooling fan in low or high speed mode by turning radiator cooling fan relays No.1, No.2 and No.3 ON/OFF according to signal from A/C refrigerant pressure sensor. | |