Thermal switch test (diesel)

The thermal switch in the diesel engine is located at the bottom of the radiator. It turns on the electric fan if the coolant temperature has reached a certain value. It is necessary to check the thermal switch if the electric fan does not turn on when the engine is hot. Prerequisites for testing: the thermostat must be in order. If the thermostat does not open, then the thermal switch cannot turn on the fan, since it is not heated by the coolant.

Attention! In 4-cylinder petrol engines, the cooling fan is turned on/off depending on the engine temperature by the engine control unit.

Disconnect the plug from the thermal switch.

Connect both terminals of the plug with a short control wire.

Turn on the ignition. If the fan is now on, the thermal switch must be replaced.

Check the tightness and contact quality of the plug on the fan motor. Check electrical wires and fan relay, see 20.4.

Screw in a new thermal switch with a new O-ring and check its function. Warm up the engine; the engine should idle until the fan turns on to cool the coolant.