A/C Compressor Torque

WARNING: This page is about a different car, the 2011 Jaguar XKR, 2011 Jaguar XK, 2010 Jaguar XKR, and 2010 Jaguar XK. However, it is still accessible from the selected car via links, so may be relevant.

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 'ACClutchInhibit' 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.