ddd777

How does one test if thermostatic vacuum switch units are in working order?

joe_padavano

You stand a better chance of getting a useful answer with your own thread rather than tacking your question onto a five year old thread, so here you are.

The TVS has two parts, the solenoid that switches vacuum off and on based on the trans switch for TCS, and the thermostatic switch that reacts to coolant temp. You can test the former pretty easily by applying vacuum and +12V to see if it switches. The thermal part is a little harder since it opens above the boiling point of water at atmospheric pressure (at 15 psi in the cooling system, water boils at over 250 F). That means you'd have to use a working fluid with a higher boiling point (oil?) to test it.

BlackGold

Of course, some failures occur at room temp. No boiling oil required.

Use a vacuum pump on the carb port. At room temp the carb port should be connected to the distributor port: air should flow, you should not be able to draw a vacuum. If you then plug the distributor port, you should be able to draw and hold a vacuum.

Next put the pump on the manifold port. At room temp it should be isolated from the distributor port. No air should flow, and you should be able to draw and hold a vacuum.

The carb port and manifold port should be isolated from each other. And under no circumstance should there be a vacuum leak when you put the pump on one of the three ports while the other two are plugged. That would indicate a leak between the cooling system and the vacuum system.

BILL DEMMER

and to test the thermostatic "switching" function, judiciously apply heat from a lighter, i would not recommend a torch.


bill