Thermostats convert a temperature into a valve position. They are used in heating systems and cooling circuits. For example, the cooling water thermostat in the water cooling of car engines specifies the valve position depending on the water temperature. At the start of the journey, the water temperature is low. At this time, the water is not led to the radiator. No cooling takes place via the open short-circuit circuit motor-water pump-motor. The motor can reach its operating temperature unhindered. As soon as the operating temperature is reached or exceeded, the thermostat opens the radiator circuit to dissipate the heat to the environment via the radiator and the fan. The motor of the fan, on the other hand, is controlled by a thermal switch. An example of use in living spaces are heating thermostats.