Electric Thermostat
The task of the thermostat is to open the coolant coil for transport of refrigerant at a pre-set temperature. In this way the temperature of the engine can be maintained at the best possible temperature regarding combustion, lubrication etc.
The thermostat's opening point can be controlled by electrically heating the wax section of the thermostat. In this way the engine's target temperature can be demand controlled. In situations with high load and/or extremely high ambient temperature the heater is activated to lower the opening point and thereby protect the engine from too high a coolant temperature.
The thermostat heating element is supplied with voltage (12 V) through the engine compartment relay/fuse box and is grounded (signal) in the control module.
The heating element of the thermostat can be diagnosed by the Engine Control Module (ECM) and the present heater signal can be read off.