Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 10, 2025 ...

When you don't know where to start you start at the beginning so here goes. Bought the coach May of this year.  Took coach in for some repairs and warranty items.  MOT informed me in doing the other requested repairs they discovered air system was not leveling and maintaining level properly.  Took a while for MOT to rectify but eventually they said they discovered some "clay" in the lines...they pulled the tanks cleaned and stated the problem was resolved.  MOT stated this was usually indicative of not changing the air dryer filter...which I had replaced before picking up coach in May. 

when setting the coach to auto level I did notice that periodically the system would expel air...but NEVER did the compressor come on to add air to the system.  Last week I picked up the coach...MOT still not done with warranty issues but I had to make this trip.  Had one day to load up the coach....we leave on Thursday night boondock at Walmart.  I park the coach, I do not level, I may have left in "trip" mode..turn off the ignition and hit the hay.  Within an hour there is the LOUD noise of the compressor coming on and it ran and ran and ran....a good 5 to 7 minutes....this happened 2 or 3 times during the night. Woke me up every @#$%^&* time it came on....I was pretty mad and tired at 6 am with a 7 hour drive ahead of me.

Get to the campground....hook up water, electric, engine still running....level the coach....put it on auto level(rapid blinking red light) and let the slide out....during the night...same thing....compressor comes on and runs for 5 minutes.  When we leave and I pull in the slide ...at the end of the slide retract process the compressor comes on.....it never had done this before.

I get home, I do not level the coach, I hit "dump" on the leveling system...dump all the air, then I go to the air drain valve ( the valve to let all moisture out of tanks...I guess..)...open that up and let more air out. SO now I am thinking NO air in the tanks, and leveling system is NOT active.
Just went outside to help the wife bring in the groceries and hear the compressor in the coach running....again.
I called MOT before leaving on my trip and spoke with tech who said the system may be trying to maintain pressure in the seal around the slide....I understand this is a possibility but the coach never did this prior to MOT working on my air system.

I am not at all in anyway mechanical, so the knowledge all of you have would certainly be wasted on me.  What I AM looking for is ideas to go to MOT with. I would love to find a link to how the air system works....is the leveling system independent of the brake system which is independent of whatever is maintaining a tight seal around the slide. I haven't got the foggiest idea of how the system works and therefore cannot speak intelligently about it or even sometimes understand what the tech at MOT is trying to tell me. 

Dave,

It's entirely possible the previous owner let the air dryer go too long.  Once that clay/white powder (desiccant) gets into the system, it contaminates more than just the tanks - it can get into check valves and then can cause the symptoms of a leak.  While it might not have behaved this way before the work (and I'm not saying there isn't a leak), it's possible the problem is migration of that desiccant that is still in the system if only the tanks were cleaned.

There are a few folks who have been through this; Jim McNeece has the most comprehensive posts with photos on the subject (that I can recall):

Desiccant powder in air system - anybody else with this experience?

2003 U320 - Phase 2 of Desiccant Powder Cleanup Complete

The system actually does occasionally need to add air to level.  Basically it first exhausts the high points and then, if it can't get level by doing that (safely - without torquing the body of the coach) it will then raise the low points.  Leveling behavior is highly dependent on the levelness/slope of the site you're in.  The system "wakes up" every 30 minutes when in level mode to check the status and will adjust level if necessary which could be any combination of exhaust and inflate.  It doesn't sound like yours is trying to relevel when it runs (you can tell if it is by looking for yellow "low point" lights on the control pad when the compressor is running) since it's going for a longer time, but if it does need to correct the level frequently that could indicate a leak in the leveling system.

The compressor running related to moving the slide is a couple of things - bringing pressure back up in the slide bladder tank after the bladder was reinflated AND to pull vacuum to deflate the slide bladder so you can move the slide safely.

If you have the leveling off and you have dumped air, then yes, if the aux compressor is running it is likely trying to pressurize the slide bladder system (you didn't open and leave open the slideout tank air drain when you opened the other tank drains, right?).  Now, you can pull the inline fuse to the aux compressor to stop this behavior (it will only stop the slide bladder function of the compressor, not the leveling aspect), but best to only do this if your coach is under cover in case it's a leak in the slide bladder system where the bladder could deflate.  And also realize you will need to put the fuse back in if you want to move the slide because you'll usually need the compressor for deflation and inflation of the bladder.

The leveling and the slide bladder system are somewhat independent.  As I mentioned above, you can dump the air and turn off the leveling, but the aux compressor will still operate to keep the slide bladder inflated.  In fact, if you have a catastrophic leak in that system or in the unload (normally open) valve on the clear bowl mounted by the aux compressor, it will run and run and run.  Since yours is only running 5 or so minutes, with hours in between, it doesn't sound like there is a major leak.  There are a couple of places that a minor leak could occur in this system - the 1/4 turn valve(s) for the slide bladder(s) is a common leak point.  Many of us have replaced them with ball valves from the air compressor department in Home Depot or Lowes.  Another is cracking in the bottom of the clear bowl with the unload valve on it (although this will only present as a leak when the compressor is running since that valve is normally open and closes only when the compressor runs). 

Now, in your 2002 do you also have the air awning?  I believe that is also fed by the aux compressor in that year, but someone with a 2002 would need to explain how it is connected to the system.  They might also be able to post an air schematic for that year (it might be different from our 2003, especially if you don't have an "air tank" switch in the group of rocker switches to the driver's left).

Dave,

We just had some work done on our air system. Our mechanic checked for leaks, Then he replaced our Living Room slide bladder, Travel Mode Vales and Solenoids, also found a couple other leaks. After picking up our RV we traveled from FL to Asheville, NC where we stayed for 20 nights. When ready to leave we had 80 psi in front and rear tanks. Our auxiliary compressor comes on every couple hours for 5 to 7 minutes. At our next stop we leveled and put the slides out. We were told st MOT when we bought our RV to leave the engine on until leveled with slides out. Compressor comes on now and then, air is released now and then.

Before this we replaced our travel height valves and linkages (the rubber ends on the linkage were fatigued and would bend) and our air dryer but could not hold air pressure. We have now been advised to replace our dryer annually. Our previous RV was an Itasca on a Freightliner Chassis and we replaced the air dryer every year.

Hope this helps,

On A & B tank pressures, governor on engine compressor generally tells that to add air when pressures drop to 90 and cut out when they reach 120. They will vary as you drive and the system uses air, but should generally be between those readings when engine is running

Also check the tank drain valves themselves with soapy water. If they hadn't been exercised in a while and now you are,  they can leak a little

Front rear and slide tank drains should be petcocks in the front driver side wheel well

Michelle/Dave,
Differences in coach models and years may be tripping you up:
2002 front and rear brake air tanks as well as the HWH aux air tank have only tank located drains (as far as I know). 

 I think that the 2003 model year Unicoach, though, was the first year to OEM install remote (rear, front and aux tank) drains in front of the street side steer tire. 

Michelle/Dave,
Differences in coach models and years may be tripping you up:
2002 front and rear brake air tanks as well as the HWH aux air tank have only tank located drains (as far as I know).  Like all other FT's, the 2002 U270, U295, U320's have the wet tank drain fitting in front of the street side duals.  I think that the 2003 model year Unicoach, though, was the first year to OEM install remote (rear, front and aux tank) drains in front of the street side steer tire.  Many owners have installed tubing extensions, aftermarket, to make the drain petcocks more user friendly, so hard to tell what might be there.
HTH,
Neal

When you walk from one end of the coach to the other it will level itself and release air from one leveling valve while adding air to the opposite leveling valve. This is normal. Turn your aux compressor off and it'll stop doing this after the air pressure goes down to about 60 psi... Don't worry, be happy!