A/C Operation Description (Petrol Model)
Precautions: General safety (00)
Upon receiving A/C switch ON signal from HVAC control unit, ECM control A/C compressor relay and radiator (condenser) cooling fan relay as described in the table below.
The A/C switch ON signal is sent from the HVAC control unit to BCM. Then it is transmitted to ECM as A/C request signal through CAN. For CAN communication system, refer to Communication System Description:M16A 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 during high engine speed | ECM stops A/C compressor by turning A/C compressor relay OFF according to signal from CKP sensor (engine rpm) to prevent A/C compressor from over-revolution while engine speed is high. | ||
| Control at engine start | ECM stops A/C compressor temporarily by turning A/C compressor relay OFF according to signals from CKP sensor (engine rpm) and others to stabilize engine idling speed immediately after engine start. | ||
| 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. |
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| 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. |
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| Radiator (condenser) cooling fan relay control | A/C refrigerant pressure sensor and wheel speed sensor | ECM drives radiator cooling fan in low or high speed mode under the following conditions by turning radiator cooling fan relays No.1, No.2 and No.3 ON/OFF according to signals from A/C refrigerant pressure sensor and wheel speed sensor when A/C compressor relay is ON.
•Low speed mode (Radiator cooling fan relay No.1 ON)
—Vehicle speed is less than specified value.
•High speed mode (Radiator cooling fan relays No.1, No.2 and No.3 ON)—Vehicle speed is more than specified value and refrigerant pressure more than specified value. —Wheel speed sensor malfunction is not detected.
—Refrigerant pressure more than specified value.
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