Radiator Cooling Fan Temperature Sensor / Switch: Testing and Inspection

Fig. 47 Coolant Temperature Switch Check:

1. Remove engine coolant temperature switch from radiator, then immerse switch in warm water or oil.
2. Connect a suitable ohmmeter across switch, as water or oil is heated the switch should close at approximately 185 degrees F and as water or oil cools the switch should open at approximately 171 degrees F.
3. If not within specifications, replace coolant temperature switch.