Radiator Cooling Fan Temperature Sensor / Switch: Testing and Inspection

Fig. 1 Testing thermo switch (typical):

1. Remove thermo switch as outlined above.
2. Connect suitable ohmmeter across switch terminals, then immerse lower part of switch in water, Fig. 1. Ohmmeter should indicate an open circuit.
3. Place thermometer in water and heat. When water temperature reaches approximately 194°F for thermo sensor No. 1 or 212°F for thermo sensor No. 2, switch contacts should close and the ohmmeter should indicate continuity.
4. If switch does not operate properly, replace it.