Thermo-Vacuum Switch

1. With the engine coolant temp below 10°C (50°F), or with the thermo-vacuum switch removed from the car and cooled, connect a vacuum pump to the angled connector of the thermo-vacuum switch.
2. Momentarily seal off the straight hose connection and apply vacuum to the angled connection.
3. Open the straight connection, and the vacuum should release (switch should be open when cold).
4. If the switch is not open, replace it.