Air Conditioning (A/C) Compressor Torque

WARNING: This page is about a different car, the 2012 Land Rover Range Rover Sport and 2011 Land Rover Range Rover Sport. However, it is still accessible from the selected car via links, so may be relevant.

The automatic temperature control (ATC) module uses refrigerant pressure, evaporator temperature and engine speed to calculate the torque being used to drive the air conditioning (A/C) compressor. The calculated value is broadcast on the medium speed controller area network (CAN) bus for the engine control module (ECM), which uses the calculated value for idle speed control and fueling control. The automatic temperature control (ATC) module also compares the calculated value with a maximum air conditioning (A/C) compressor torque value received from the engine control module (ECM) over the medium speed controller area network (CAN) bus. If the calculated value exceeds the maximum value, the automatic temperature control (ATC) module signals the refrigerant solenoid valve to reduce the refrigerant flow and so reduce the torque being used to drive the air conditioning (A/C) compressor. By reducing the maximum air conditioning (A/C) compressor torque value, 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.