In-Car Turn-On Switch

A thermostatic switch enclosed in a small plastic cylinder located just behind the faceplate. It senses car interior temperature and will close and turn on the system if that temperature is above approximately 75°F (24°C). This will occur even if the engine coolant is cold and the other turn-on switch located in the right cylinder head, is cold. This provides immediate cooling in a hot car that has not been run for some time.