There is a small 12 volt vacuum pump located in the cavity behind the cloth flap under the stairs. It tends to come on for 15 or 20 seconds when I turn on the ignition. I did not find any reference to it on the air system diagram. Can anyone tell me what its function is and what it powers?
Thanks, Richard
Search is your friend ;) It operates the dash vent air direction/position
Vacuum Generator finally quit (http://www.foreforums.com/index.php?topic=10325.0)
For the benefit of other readers, this electric vacuum pump is located in the nose of some Foretravel coaches, like my U300, outside the firewall near the driver's feet, and on some older coaches it's an air powered vacuum pump instead of an electric pump.
My U320 2001 had the air powered vac pump under the front steps, Had it changed to the 12VDC model, turned out was not needed, but feel better hearing the pump when I turn on the ignition every few days, it holds vac very well.
Was chasing an issue with the a/c ducting, problem was found at FOT, a wire worked off a relay deep in the maze, but the tech knew exactly where & how to go, made it look very simple & easy. Gotta love sperience.
...do you still have the air powered vacuum generator? I want to change mine from electric to air at some point. The electric pump is expensive and I've already replaced it once. The air powered pump has no moving parts and should last forever.
Hi Scott,
My air driven vacuum generator under the step died a few yeaers age. You might consider going to an automobile salvage yard to find a used electric vacuum pump. There I found an older Cadillac pump for about $30. Works great - hey, vacuum is vacuum. I hear it run for a about 3 seconds when the ignition key is turned on. It solved the problem of A/C vent doors for the dash air distribution system.
My electric pump works, I was just planning ahead to the day when it dies again... How did an air powered vacuum generator die? Isn't it just a venturi with no moving parts?
If I not mistaken it really doesn't die there is a can with the pump which over time gets a leak because of rust. replacements are built different.
Our vacuum pump, up front of the "firewall" runs whenever the ignition is on. Even if I disconnect the hose to the reservoir can and hold my thumb over the end of the hose. What causes the pump to shut off?
There should be a vacuum switch on it when it gets to the set point it shuts off. The vacuum canister stabilizes and stores the vacuum so your vents do not open and close until you move your dash switch lever.
Sorry, but I could not find any switch anywhere so I put a toggle switch on the dash just so I could shut the darn thing off! That was last fall before putting the coach in storage.
If the vacuum reservoir leaks you can go to a junkyard and buy any suitable used vacuum reservoir and install it in the vacuum line near the pump.
Our vacuum reservoir is a plastic ball shape. Even disconnecting the vacuum hose where it comes out of the vacuum pump and then holding my thumb/finger over the hose outlet on the vacuum pump does not cause the pump to shut off. It does build up suction, but I didn't see any place where there would be a vacuum actuated switch.
I did remove enough stuff up under the liftup dash to see the vacuum diaphragm actuators were working when I pushed the different selector buttons on the Ford climate control so I must have enough vacuum there. I also disconnected each hose at the diaphragms and found vacuum present when testing each hose.