Compressor Clutch Control: Notes

The compressor clutch is controlled by the BCM through the ECM from inputs to both the ECM and the BCM.

ECM inputs consist of BCM data, power steering cut-out switch, engine coolant temperature, engine RPM and throttle position sensor. BCM inputs consist of ECM data, ECC setting, outside air temperature, in-car temperature, sunload sensor, vehicle speed, low refrigerant pressure switch, A/C high side temperature and A/C low side temperature.

The voltage source to the compressor clutch is from the HVAC fuse, through the power steering cut-out switch and the low pressure switch, both of which must be closed.

When all inputs to the BCM are within the calibrated values, the BCM signals the ECM to allow the compressor clutch to engage. The ECM then sends a signal to the power module, which completes the circuit to ground and engage the compressor clutch.

Through interaction of the BCM with the ECM, the compressor clutch will engage when, the climate control is set to "A/C", "AUTO", "BI-LEVEL" or "DEFOG", or the outside temperature is above 45°F (7°C), or the climate control is set to "AUTO", or "DEF".

Once engaged there are 2 modes of compressor clutch control for the minimum time the A/C clutch will stay engaged.