Radiator fan thermostatic switch - removal, checking and refitting

Cooling and heating systems / Radiator fan thermostatic switch - removal, checking and refitting

1 Drain the cooling system.

2 If the thermostatic switch is being removed because the fan is not operating and the switch is suspect, check the fan fuse first, before removing the switch.

3 To remove the switch, disconnect the leads from the terminals and unscrew the switch.

4 Connect a test bulb and battery across the switch terminals and then immerse the sensing part of the switch in a container of water. Heat the water and, using a thermometer, check the temperature of the water when the bulb lights up, indicating the switch is functioning. The switch should operate at approximately 194ºF (90ºC). Allow the water to cool and check that the switch cuts out at 185ºF (85ºC). Renew a faulty switch.

5 Refitting of the switch is the reverse of the removal procedure. Always fit a new O-ring on the switch.