Thermovalve Test Procedure

[Paulporsche]

There is a possibility that my WUR is not operating correctly because of a faulty thermovalve. It should provide vacuum to the bottom of my WUR (045/'79 SC).

If I follow the same procedure for testing contro; pressures, and remove the hose from the WUR should I feel the suction in the line?

If no suction is the thermo valve bad?

Is there another test for it? Should I get a resistance across its 2 terminals?

[snbush67]

Opens at 81 degrees (ambient temperature in engine compartment)
When it is closed it does not allow vacuum to the WUR which creates a rich mixture to prevent backfiring when cold.

To test it put it in you fridge attach a hose and try to blow or suck air through it, then warm it up above 80 (hold it in your arm pit) and do the same. This will tell you if the bimetallic disc is operating correctly.

You could also simply connect a 12 V power source to it and you should feel it heat up immediately, and hear the disc click open from cold to warm or closed from warm to cold.

From Jim Williams CIS Primer;

Holds off vacuum from the warm-up regulator when engine is started cold ('77 - '79 engines). Power is applied to the thermal valve when engine is started, and approximately 30 seconds later, the valve opens. When the valve is open, vacuum to the WUR is then determined by the intake manifold. --The vacuum hold off results in a mixture richening at warm-up. The inner hose connects to the intake vacuum source and the outer hose to the WUR.

Failure mode: An open circuit in the internal heater will keep the mixture from properly leaning out as the engine warms.