A/C Compressor Torque

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2015 Jaguar XFR, 2015 Jaguar XF, 2014 Jaguar XFR, 2014 Jaguar XF, and 2013 Jaguar XFR. However, it is still accessible from the selected car via links, so may be relevant.

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

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