Auto A/C Terms - Glossary
Cycling Clutch A/C System

On any auto A/C system, the compressor operates in order to pump and circulate the refrigerant. In order to reduce the use of the compressor and save resources like fuel, some A/C systems are designed to turn the compressor off when not required. Those A/C systems are referred to as cycling clutch A/C systems. The major difference between these systems and others is that the compressor clutch with engage and disengage as required in order to maintain the proper flow of refrigerant.

In earlier days when vehicle manufacturers were concerned about fuel economy, it was determined that cycling the compressor on and off would help reduce the load on the engine and thus provide a savings in fuel consumption. We have no comment on the fuel consumption, however, the cycling of the compressor does work well and will not reduce A/C system cooling performance.

The compressor cycle is controlled by either a temperature or pressure sensing switch. That switch is usually located somewhere between the evaporator outlet and the compressor. In some cases, temperature sensing bulbs are actually inserted into the fins of the evaporator.

When the low side pressure or temperature becomes too low, and there is a risk of freezing the condensation on the A/C evaporator, the switch would cycle the compressor off. When the compressor cycles off, there no longer is any compressor suction on the low side of the system and the temperatures or pressures are allowed to increase. When those temperatures or pressures increase to the point where more cooling is required, the switch will cycle the compressor back on, creating a suction on the low pressure side of the system. That suction reduces both pressures and temperatures creating the cooling effect of the air entering the vehicle.