Car A/C Expansion Valve System
The expansion valve type of air conditioning system is the oldest design and most common cycling clutch type system. The compressor clutch is cycled on and off by the thermostatic switch. The thermostatic switch is located on or near the evaporator, where its sensing tube can “feel” the temperature of the evaporator coils. The switch engages or disengages the compressor clutch to maintain the correct evaporator temperature. This process keeps the cooled air entering the vehicle at a constant temperature. This type of system was once typical of OEM air conditioning systems.