Engine - Coolant Temperature Sensor/Switch: Testing and Inspection

Fig. 11 Testing Thermo Switch.:

1. Remove thermo switch as outlined above.
2. Connect suitable ohmmeter across switch terminals, then immerse lower part of switch in water.
3. Place thermometer in water and heat, Fig. 11. When water temperature decreases to 176-187°F continuity should not exist. When water temperature increases to 189-199°F continuity should exist.
4. If switch does not operate as indicated, replace.