Thermo Time Switch: Testing and Inspection

Cold Start Components:

1. To test the Termo-time Switch make sure engine coolant temperature is below:

86°F (30°C)

Preferably the engine should sit for several hours or overnight if possible to ensure low engine temperature.
2. Disconnect the coil wire from the center tower of the distributor cap and connect it to ground, using a jumper wire.

Thermo Time Switch Testing:

3. Disconnect the cold start valve harness connector and connect a test light across the connector terminals, as shown in image.

Thermo-time Switch Graph:

4. Actuate the starter while observing the test light. The test light should light for several seconds, then go out. The amount of time that the light should stay on depends on coolant temperature, see graph.
5. If the test light does not light, it is either because voltage is not reaching the connector due to faulty wiring, or because the Termo-time Switch is faulty.
6. Disconnect the harness connector at the Thermo-time Switch and check for continuity between the wires that run from the cold start valve harness connector to the Thermo-time Switch harness connector.
7. Check for battery voltage at the Thermo-time Switch harness connector and the cold start valve harness connector (with test light grounded to the engine), while actuating the starter.
8. If the above tests are OK replace the Thermo-time Switch.