Thermostatic Vacuum Switch

Evaporative Emission Control System:

- Start test with cold engine (coolant temperature below 46° C, 115° F).
- Remove both hoses from TVS and plug. Check that no air passes between the TVS ports.
- Attach a hose to either TVS port and warm up engine. Blow on the hose and check that air passes between the TVS ports when the specified temperature is surpassed.
- As an alternative, a similar test can be run with TVS removed from vehicle and heated in a pan of water.
- Replace TVS if found defective.