A/C Compressor Torque

The automatic temperature control (ATC) module transmits refrigerant pressure and air conditioning (A/C) compressor current values to the engine control module (ECM) over the medium speed then high speed controller area network (CAN) bus, using the instrument cluster as a gateway. The engine control module (ECM) uses these values to calculate the torque being used to drive the air conditioning (A/C) compressor. The engine control module (ECM) compares the calculated value with its allowable value and if necessary forces the automatic temperature control (ATC) module to inhibit the air conditioning (A/C) compressor by transmitting the 'AC Clutch Inhibit' controller area network (CAN) message. This forces the automatic temperature control (ATC) module to reduce the drive current to the air conditioning (A/C) compressor solenoid valve, which reduces refrigerant flow. This in turn reduces the torque required to drive the air conditioning (A/C) compressor.

By reducing the maximum air conditioning (A/C) compressor torque, the engine control module (ECM) is able to reduce the load on the engine when it needs to maintain vehicle performance or cooling system integrity.