THE COMPRESSOR – HOW DOES IT WORK?

 The compressor sucks in the high-temperature, low-pressure gaseous refrigerant from the evaporator and compresses it into a high-pressure state, prior to discharging it into the condenser. The compressors in most cars are belt-driven and comprise several pistons inside to suck in and expel the refrigerant. These can be activated by an electromagnetic clutch, via a relay. To reduce engine load and fuel consumption (as well as controlling evaporator temperatures), they can cycle the clutch on-and-off repeatedly.

An alternative is to use a dedicated ECU to control a variable displacement compressor. This works by altering an internal swash plate’s position electrically, which varies the displacement of the pistons; effectively altering each cylinder’s cubic capacity. By reducing the compressor’s output, the reduced engine load benefits fuel consumption and CO2 emissions. By keeping the compressor running at a reduced capacity, it's easier to maintain the cabin’s conditions after the desired comfort settings are reached.