Thermo Time Switch: Testing and Inspection

Fig. 9 Thermo Time Switch:

1. Disconnect electrical connector from switch and connect test lamp between battery positive terminal and terminal W on switch, Fig. 5.
2. Test lamp should light with coolant temperature below 35°C (95°F), and should not light with temperature above 35°C (95°F).
3. Connect ohmmeter between switch terminal W and ground, Fig. 5. With coolant temperature below 30°C (86°F), meter should indicate continuity; with temperature above 104°F, meter should indicate no continuity.
4. Remove switch and cool sensor element to approximately 0°C (32°F).
5. Connect ohmmeter between switch terminal W and housing, connect negative battery terminal to housing using jumper wire, then connect positive battery terminal to switch terminal G.
6. Meter should indicate continuity for 2 - 6 seconds, then infinite resistance.
7. If thermo time switch fails to perform as outlined, switch should be replaced.