4wd vacuum solenoid function
I was checking out the quality of the vacuum source to my front hubs after changing front axles, u-joints, seals, and hubs, all of which were necessary do to lack of proper maintenance in my 2002 F350 4x4 w/7.3.
I discovered the electric vacuum pump cuts out at around 13 inches of mercury, then cuts back in as vacuum drops.
I also discovered solenoid that directs vacuum from the vacuum reservoir to the hubs was as first, then stopped allowing vacuum. When I bypassed the solenoid, both hubs locked as they should. When I reconnected the solenoid, the vacuum was no longer present at the hub. I see there three wires connected to the solenoid, don't know where they go.
So, the solenoid worked, allowing vacuum to the hubs, then it didn't work and the vacuum bled off the hubs and they disengaged.
I don't know if the solenoid is faulty, or it is supposed to function this way for some reason.
Anybody have knowledge on how this solenoid is supposed to act?
Logic says as long as the dash switch is in 4wd, the solenoid should pass vacuum.