Vacuum pump ?

[Murk]

It's a 99 powerstroke. 65k miles. 4x4 dually F-350

The vacuum pump runs continuiously. Traced lines from canister to a switch(?) just adjancent to the canister. Unplug vacuum lines from the switch and plug line and pump stops. This switch has a 3 conductor plug attached to it. What is this part? What does it do? What controls it and where does it gets it's signals.

The switch has 2 vacuum ports. One of which will not or does not close and thus makes the pump run.

[Murk]

Stumped ya huh? I'd still like to know what this valve is and does.

I took the valve out and slammed it against the workbench a couple times. Also cleaned the electrical contacts (where it plugs in) also cleaned the plug. Slapped it back in. Fired the motor up and the vacuum pump develops vacuum and shuts off. Took off for a test drive. Seems to have all the power and function. We will see if the problem returns.