1. The thermal switch is screwed into the coolant inlet fitting. It turns on the electric radiator fan when the coolant reaches a certain temperature. The switch should be checked if the fan does not turn on when the radiator is hot. Test conditions: Check the electrical wires, relay and fan motor according to the diagram. The thermostat and pressure reducing valve in the radiator cap are in good condition. If these elements are faulty, the thermal switch will not be able to turn on the fan, since it is not heated by the coolant.
2. Disconnect the plug from the thermal switch.
3. Unscrew the thermal switch.
Warning! Coolant will leak from the hole in the inlet fitting. Place a container underneath to collect the liquid.
4. Hang the thermal switch in a container with water. Heat the water slowly.
5. Use an ohmmeter to check the current flow through the switch. At a temperature of +91°C, the current should flow.
6. Leave the water to cool and check that the current stops flowing at a water temperature of +84°C.
(Content based on information from: mazbook)
7. If the values do not match the required values, the switch should be replaced.
8. Screw the switch on new with a gasket with force 10 Nm.
9. Fill with coolant.
10. Warm up the engine and let it idle until the fan comes on. Check the coolant level again.