mysterious pump

[encantotom]

howdy,

once in a while i hear a pump come on for 20-30 seconds coming from the very front of the coach. it is not the 110v or 12v compressor.

that is when the coach is just sitting in the driveway with nothing on.

i have yet to find it because by the time i look it is off.

is there a vacuum pump or does the hydraulic pump for the slides have power to it all the time? doesnt seem like it should.

tom

[folivier]

Tom, it sounds like a catnip pump.................

[tuga]

Tom,

Assuming that your 120v air compressor pump switch is located around the microwave,
try turning it off from inside the coach when you hear it kick on. That would be quicker than running outside to try to find it.

Hope this helps.

[encantotom]

it is not the compressor. it is off.

tom

[HoosierDaddy]

Hi Tom.....I love these mystries! B-)
I'm thinking vacuum pump???

[prestadude]

It is likely a vacuum pump. I had my rig in to Newell for service with two complaints,1) there was something constantly running (sounds like a compressor) underneath my feet in the drivers position and 2) air flow from the dash vents was poor. Turns out the vacuum pump (which sounds just like a 12V compressor) was bad and could not generate a vacuum and consequently ran all the time. The vacuum is used to move the blend doors in the dash vent system. Replacing the vacuum pump fixed both problems.

[encantotom]

that is my guess as well. i replaced the vacuum pump on my 90 (it was air powered and i put in a ford 12v pump) but it only had power to it when the ignition key was on. why would my 2002 have power on all the time?

tom

[RussWhite]

My vacuum pump is supplied power only when the ignition switch is on. Is there any possibility it is the fan for the inverter?
Russ

[encantotom]

hi russ, i know the fan on the inverter and it is much quieter and back in a bay. this is much louder pump sounding noise coming from the front.

i have to just spend some time looking for whatever it is.

thanks

tom

[RussWhite]

Hi Tom,

You kind of let us hanging on this one.

My vacuum pump, located way up inisde the area housing the front manifold, air horns, driver's side head lights, etc. has started to run continuously when the ignition switch in on or in the accessory position. I know I need to round up a vacuum gauge, but a quick check made by pinching the hose off directly downstream of the pump did not cause the pump to stop. From that I think I am probably looking at a bad vacuum switch or pump - and they may be an integrated unit.

Has anyone crawled far enough up in there to see what kind of pump is there?

I'll try to post back here on whatever I figure out. As always, I am glad to have the help of the expereince of folks who have gone before.
Russ

[encantotom]

Hi Russ. It is the 12v vacuum pump. It operates normally. Does not run all the time. Tom

[RussWhite]

With the hose clamped off, mine is now running all the time. There is sufficient vacuum to operate the controls and I can feel its pull on my skin, but without a guauge don't know the actual amount. Since I am close to embarking on a trip I just went ahead and ordered a replacement. I figure both the pump and switch are integrated into the one small package, so a new Dorman 904-214 it is. Cost was about $90 with tax at local auto parts store and $63 delivered from RockAuto.

I'll let you all know if this does not work out for any reason. Russ