Radiator Cooling Fan Temperature Sensor / Switch: Testing and Inspection

Fig. 1 Testing thermo switch (typical):

1. Disconnect battery ground cable.
2. Drain cooling system into suitable container.
3. Disconnect thermo switch wiring, then remove switch
4. Connect suitable ohmmeter across switch terminals, then immerse lower part of switch in water, Fig 1. Ohmmeter should indicate an open circuit.
5. Place thermometer in water and heat. When water temperature reaches approximately 185 deg. F on 1984-85 models or 194 deg.F on 1986-88 models, switch contacts should close and the ohmmeter should indicate continuity.
6. If switch does not operate properly, replace it.