Cars with a gasoline engine
The thermal switch turns on the electric radiator fan when the coolant is heated to a certain temperature. The switch should be checked if the heatsink is hot and the fan does not come on.
1. Check the wiring diagram for the electrical wiring of the thermal switch and the fan motor. The thermostat and safety valve should be in order. If the thermostat or safety valve is defective, then the thermal switch does not work because it is not heated by the coolant.
2. Drain the coolant.
3. Disconnect the thermoswitch plug. The thermal switch is screwed into the bottom left radiator tank.
4. Unscrew the thermal switch.
5. Place the thermal switch in a container of cold water and slowly heat the water by connecting an ohmmeter to the thermal switch contacts (see illustration). When off, no current should flow (resistance is «infinity»). When on, current must flow (resistance = 0 ohm). The thermal switch makes a loud click when switched on. The thermal switch must switch on at a temperature of approximately 100°C.
6. Let the heated water cool down and check that the thermal cut-out switches off when the water temperature is about 95°C.
Replace the thermal switch if this does not happen.
7. Install a new thermal switch, replacing its old seal with a new one and tighten it with 20 Nm.
8. Connect the thermoswitch plug and fill the expansion tank with coolant.
9. Warm up the engine and let it idle until the thermal switch trips.
Visitor comments