Electrically Heated Thermostat The electrically heated thermostat is used to regulate the engine coolant temperature. The thermostat regulates the coolant temperature depending upon engine load and vehicle speed. This allows the engine coolant temperature to be raised when the engine is operating at part load. Raising the coolant temperature while the engine is at part load has a beneficial effect on fuel consumption and emissions. If a conventional thermostat with higher constant operating temperature is used, poor response when accelerating and in traffic could result. The thermostat is controlled by the ECM is response to engine load against a 'map' stored within the ECM. The map is based upon the following inputs: l Engine load l Engine speed l Vehicle speed l Intake air temperature l Coolant temperature. The thermostat unit is a one piece construction comprising the thermostat, thermostat housing and heater element. The housing is of a die-cast aluminium. The electrical connection for the heater element is housed in the body. The heater element is an expanding (wax) element.