Car Thermostatic Switch
The thermostatic switch used on some systems controls the compressor in accordance with the evaporator temperature. The switch uses a temperature-sensing capillary tube to sense evaporator temperature. The capillary action causes the switch contacts to open or close in accordance with the evaporator temperature. The switch operates within a predetermined temperature range, switching the compressor off at a preset temperature and back on again at another preset temperature. Some switches are adjustable so that the compressor switching can be controlled in accordance with the requirements of the system and the vehicle occupants.
When the temperature in the evaporator approaches freezing, the thermostatic switch contacts open, disengaging the compressor clutch, which stops the compressor. This allows the temperature in the evaporator to rise (because of the reduced refrigerant flow) until, at the predetermined temperature, the switch contacts close, engaging the compressor clutch, and restarting the compressor.