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Topic: Vacuum pump or??? (Read 453 times) previous topic - next topic

Vacuum pump or???

When I had the problem with the D-2 a couple of weeks ago, the tech asked why there was a vacuum pump running up front. I didn't know, but from what I read on the forum it sounded like it has something to do with the automotive a/c system. Today when I put out the awnings I heard it running - and the engine is off. When I got back in I checked that the key is off (it is). Any ideas about this? The storms aren't going to get her until late this afternoon or evening, so I've got some time to work.

Re: Vacuum pump or???

Reply #1 –
Sounds like some "creative wiring" might have been done? 

My electric vacuum pump, located under the step well, runs only to build vacuum to manage switching the airflow (from defrost to dash vents).  But that only functions when the ignition is on, and the automotive system (A/C or vent or heat) is on.  A common source of failure with tiny air leaks making the included pressure switch flick on and off, but sounds like you might have a vacuum leak AND someone wired it to have power with the ignition off.  But then, I am describing what it is like in a 2002.  Dunno the specifics of a 1993.
The selected media item is not currently available.Brad & Christine Slaughter
Was:  1990 U280 36'
Was:  2002 U270 36' (With a bathroom door) Build #5981
Is:  2021 Leisure Travel Van Wonder 24RL
2015 Jeep JKU, 2003 S10 QC 4x4 or 2017 C-Max
Lake Havasu City, AZ (or Gillette, WY)

Re: Vacuum pump or???

Reply #2 –
Yes, vacuum pump is for the dash ventilation controls but it should only run when the ignition is on and it should not run continuously (not clear form your post if it is).  There's a pressure (vacuum) switch that turns it on only long enough to maintain the minimum vacuum for the vent controls.  With ignition off and vac pump running I'm wondering if your dash solenoid is stuck?  (But I'm sure you would notice a dash lights or gauges)  I would not let it continue to run - pull fuse for it until you can figure out what's wrong.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Vacuum pump or???

Reply #3 –
I just went outside and it is still running. It hasn't run before when the engine is off, so something has changed. Dash lights and gauges are normal. I'll see if I can find a fuse for it and pull it. Of course, that means moving the television, so I'll have to make sure that Jo Ann can go a few minutes without the tv.

On edit: pulled the fuse and the pump is silent. Now to figure out why.

Re: Vacuum pump or???

Reply #4 –
David, since we have similar models looking forward to your research.

I heard a pump but it was the leveling pump :))
The selected media item is not currently available.
My advice and experiences are Free, you decide if they are worth anything .

John - driving Old Faithful
1994 U280 GV
C8.3, Banks, Pacbrake, 900 watts, Resonator, XLHD tow dolly
Retired Army Warrant Officer

Life is what you make of it - if it is lemons, make lemonade!
Former Coaches:
1988 GV 40' ORED 300HP CAT - 9 years
1990 Winnebago LeSharo - 3 years
2000 Newmar London Aire - 3 years (#18 of 23 produced)

Re: Vacuum pump or???

Reply #5 –
Problem solved, at at no expense. I pulled the fuse, and all was quiet. When I went out to poke at it, the noise was present, with the fuse OUT! Strange! I then pulled the wires from the relay and the noise continued. How can an electric motor run when it doesn't have any electricity to it? I happened to bump up against the grill and the noise stopped. It didn't take long to figure out that I could make the noise come and go just by touching the grill. Since the front a/c is running that is probably the source of the noise, NOT a vacuum pump that is running when it shouldn't.

Back to monitoring the coming storms.