System Operation
When A/C switch, AUTO switch, DEF switch is pressed or when shifting mode position D/F, unified meter and A/C amp. transmits A/C switch signal and blower fan motor switch signal to ECM, via CAN communication. ECM judges whether compressor can be turned ON, based on each sensor status, refrigerant-pressure sensor signal, throttle angle, etc. If it judges compressor can be turned ON, it sends A/C compressor request signal to IPDM E/R, via CAN communication.
Upon receipt of A/C compressor request signal from ECM, IPDM E/R turns A/C relay ON to operate compressor.
When sending A/C compressor request signal to IPDM E/R via CAN communication line, ECM simultaneously sends A/C compressor feedback signal to ECM via CAN communication line.
ECM sends A/C compressor feedback signal to unified meter and A/C amp, then, uses input A/C compressor feedback signal to control air inlet.
Compressor Protection Control
ECM makes the A/C relay go OFF and stops the compressor when pressure on the high-pressure side detected by refrigerant pressure sensor is over approximately 3,119 kPa (31.8 kg/cm2 , 452 psi), or below approximately 118 kPa (1.2 kg/cm2 , 17 psi).
Low Temperature Protection Control
Unified meter and A/C amp. turns compressor ON or OFF as judged by a signal detected by ambient sensor and intake sensor.
When ambient temperature is higher than -2°C (28°F), the compressor turns ON. The compressor turns OFF when ambient temperature is lower than -5°C (23°F).
When intake air temperature is higher than 1°C (34°F), the compressor turns ON. The compressor turns OFF when intake air temperature is lower than -5°C (23°F).