Dumping Air

[swebster]

OK this just started happening. The air system is dumping air at the compressor until it's empty. Here is what I've observed so far:

If the compressor switch is on in the dash and I have the ignition on then the compressor runs continuously with no dump.

If I turn the compressor switch off with the ignition on it dumps

If I then turn the ignition switch off it stops dumping.

I'm going to look in the coach manual tonight (it's at home) but does anyone have ideas?

This started after I pulled her out of my driveway last weekend to take he back to the office for storage. I do have a big ramp on the drive and the tags can get into some "extreme" angles going in and out at an angle - could I have bent, broken a leveling valve? I quick look under the coach and I don't seen anything obvious broken.

[thenewkid64]

Sounds like a valve is stuck in the open position and the running compressor is keeping ahead of the outflow.

One way to see what one it is, park it and allow the air to dump. Slide under and thump or squeeze each bag. The one that is flabby or down on the bell is the one to check.

The leveling valves are electrically activiated so the key on/closed thing makes sense, sort of.

When I was having trouble I ended up allowing all of the air out of the system and then filling from a high output compressor with the key on. This did overfill the bags a bit, but as soon as I disconnected the air the dumps were able to catch up and the coach leveled. Are you sure the valve is closing when you turn on the key, or does the compressor drown out the sound?

It could be that your over pressure pop off is stuck open.

I just re-read your post. Forget all the other stuff. It sounds like your check valve in the compressor has failed. when you turn on the powwer to the compressor it creates enough pressure to reclose the valve. no power no pressure. You can add an in line one to save the $$ of the new compressor.

[swebster]

Brett,
Thanks. Yeah all the noise is coming from the compressor. I'll check and see. I was wondering if it could be frozen moisture in a overflow valve or something, etc. I'll check it out and get a check valve.

[swebster]

OK, some more info: there is a little black plastic/metal valve mounted on an angle bracket. It has two wires on it; one to ground the other to what looks like a pressure regulator (with a spring and a contact bar on it). This valve is where it's blowing off air. It's definitely down to 0 psi now.

One more note that may or may not be related. When I pulled out of the driveway last time (remember it was working in the driveway) I heard a "clunk" sound from the driver's side rear. My suspension makes these noises sometimes with big weight shifts (full left to full right in a parking lot for example) so I didn't think anything of it. Not sure if it's related but I’m racking my brain on this one.

Does anyone know what the valve is and what triggers it to dump air? I want to trace it upstream but I’m new to air systems so I’m not even sure what would trigger the valve.

Don't know about you but something always seems to break right before a trip for me! Just found out I'm headed to St. Louis Sunday night. This must be payback for fixing the generator for under $8 bucks!

[thenewkid64]

Steven,

I would guess that the black valve is a pressure relief valve of some sort. The 325/345 series have a lot more air stuff on them than my ancient 78

Is the outlet from this valve something that can be capped with a threaded cap? This would only be a temporary thing until you can get a new one from a truck supply house. I would be concerned with removing it form the system because I don't know what the wires do.

Fred? Dennis? you guys out there? I know the compressor normally comes on at start and runs for a minute, but normally the system maintains pressure while parked so what is happening does not sound normal

[swebster]

Brett. No threads to cap it. I had a co-worker cycle the compressor switch while I stuck my head under the bed and listened and felt for air. When he turned it on it was not leaking at all so it seems operational (at least on its own). I think something else in the system is triggering it to dump like that.

I went back and read some post from Dennis about how the levelers dump the air when they go down. I am thinking this might be related to my issue. I didn't drop the levelers before this started but I remember hearing an air dump before when the rear jacks were down this summer (I rarely drop the jacks).

The wiring digram for the jacks shows warning switchs on each jack wired back to the light panel. All of thisi s wired into the ignition. There is nothing in the diagram that shows if AS wired the air system into the jacks but since it cycles with the switch/iginition my thinking is more toward some kinds of electrical trigger then a bent or broken leveling valve on the tags.

I plan to cycle the jacks tomorrow to see if there is something as simple as a stuck (or fozen) microswitch back there. I thought the chassis manual was here at the house but its back in the 345 (Arggghh!)

I'm making all of this up in my head as I go so I would love more feedback from everyone on this.

[jthew1]

Originally posted by swebster@myrvadvanta

Does anyone know what the valve is and what triggers it to dump air? I want to trace it upstream but I’m new to air systems so I’m not even sure what would trigger the valve.

Me too, but the symptoms sound familiar to my 86 - 345, so take the following for what it's worth:

there is a little black plastic/metal valve mounted on an angle bracket. It has two wires on it; one to ground the other to

You're getting close now.

what looks like a pressure regulator (with a spring and a contact bar on it).

That's likely the culprit. It has a plastic cover with an embossed Square D and Pumptrol. Has a high and low adjustable cutoff setting for the compressor. Same is used on water well pumps and are readily available and inexpensive at any hardware. You can clean up the contacts & springs and even over-ride it by pushing on the contact bar with an insulated screwdriver. The symptoms described in your previous posts re: the ignition switch, etc. sound very familar.

I heard a "clunk" sound from the driver's side rear

Don't run it until it is fixed, it cost the PO of my coach a whole new tag axle assembly.

Don't know about you but something always seems to break right before a trip for me!

Ditto, but it may be that we leave these distasteful, misunderstood things until the last minute. Stripping & polishing is a lot more rewarding.

Have a safe and happy trip.

Regards,
Jeff

[jthew1]

Steven:

Well after re-reading all the posts, re-thinking the situation (while contemplating my navel) and popping the top on another green bottle (Heineken), I've got to agree with those who suspect a malfunctioning "check valve" (plastic-metal valve mounted on an angle bracket).

I have this problem intermittently, but the solution has always been to let the compressor run with the ignition switch on for a few minutes; then cycle the switch (on-off-on) and that stops the compressor and air dumping.

If that doesn't work, hit it with a hammer; if that doesn't work get a bigger hammer

Good Luck,
Jeff

P.S. I don't believe the electric/hydraulic jacks are connected in any way to the air bag suspension. The venting/pumping you hear when operating the jacks is simply the air suspension compensating for the change in axle height.

[swebster]

I thought I would provide an update on the air dumping issue. The air system somewhat mystified me in the beginning but I've learned a lot about the air system during this process and wanted to pass it along:

Here is the basic concept (took me all day to figure this out but at least I spent it in the rear bedroom with the furnace on instead of under the coach on a gravel driveway)

The air system has two 12V leads coming into it. One is from the ignition on and the other is a constant 12V source. Basically there is a electrically operated dump valve wired into the contacts on the high pressure cutoff switch.

If there is no 12V power, the switch opens and dumps air. When the ignition is on and the compressor is on then this valve was getting power from the ignition side of the circuit and staying closed. However when I killed either the pump or the ignition (and in turn the pump) no 12V power, valve opens, dumps air.

After an afternoon of removing and testing for power, and jumping power in from the water pump and lot of looking at the coach manual (thanks Alan!) I realized that all of this is working perfectly. I even found a new dump valve and replaced it - same problem. The problem, I believe turns out to be in the other end of the coach!

So I went back and re-read some post about air systems and realized that the little switch and gauge on my dash my not be original. I thought all 345's had a manual toggle to turn on the compressor but apparently not. I looked at the wiring and it looks like typical PO nonsense (no kidding five separate wires butted together with an inline fuse and jammed into the block with a blade connector)

I also remember messing around under the dash last weekend (when my troubles began) trying to figure out how the CB was wired. So I may have disconnected something, but I'm also thinking that this PO switch was installed to turn the constant 12V on an off. I’m not sure why yet – but there are a lot of PO related moments in the 345. I’m sure he had a reason at one point I just don’t know what it was.

I'm still not out of the woods yet, but I did manage to get her up to pressure so that’s good. I'm letting her run now to make sure the high pressure cuts off at 105 psi before I leave on this trip.

BTW - I removed the bed plywood while working on this and highly recommend doing so for work on the compressor or water pump. That access panel is way too small to get at everything and remove components. I also remounted the compressor and WP while I was in there - (much quieter now).

[swebster]

OK..after a few adult beverages I"m beginning to doubt my theories. (they have a way of doing that to me).

In retrospect I think that that valve is supposed to open to release pressure between the compressor and the check valve. I and now thinking the problem is the check valve between the compressor and accumulator tank.

Tomorrow - under the RV. Supposed to rain and sleet so that should be fun!

If this is the case then it would mean that Brett was right in his very first post about this - which would mean I would need to purchase an adult beverage for him at the next MH rally.

[zamboni]

Our MH had simliar problems when we purchased...compressor would pump up the air bags (eventually)seemed to take very long time to pump up from completely empty. During the process blowing the fuse once or twice.

Had trip planned for follwoing weekend. TICK...TICK...TICK.

Took apart the two self leveling valves, the two solenoid valves, removed all air lines, took out the compressor and checked pressures, check the pressure switch, drained the tank.

Finally to get it back operational, I by-passed the two self-leveling valves and electric solenoids. I fed both air bags from the tank, and installed a Pressure gauge, schrader air valve (similar to valve stem) in a location in the generator comparment and shut off valve so I can by-pass the on board compressor (if fails) and/or add air to the system from our garage compressor or at the service station. This did the trick for the trip...and has been working for over a year now.

I know I need to put it back to the two self-leveling valaves and the electric solenoids eventually. But each time the weather is nice enough to crawl up under the MH for a day...I'd rather take it oput camping!!!

Ya know what I mean.

[swebster]

zamboni - yeah I know what you mean. I've got my front lounge torn up right now for a remodel and I was planning on laying the new floor this weekend - but she needs to leave for St. Louis tomorrow so the air bags have my full attention.

PS - is that a rear bedroom 280 you have? Very nice!

[swebster]

OK - as usual, I think everyone is right. I pulled the check valve from the accumulator tank and its full of crud and goo. I went to PepBoys and AutoZone (Napa is closed) with no luck. Also tried the air tools section at Home Depot.

This valve has a number of reducers on it to make it work so I have to wonder if it's original to the coach. (Please see attached pic). The tank side screws into a 90 degree cast iron elbow (looks like gas line).

Does anyone have a source for these? I will stop at Parker tomorrow but since a few people have been here before I figured I'd ask around first.

[87MH]

You figured it out!!!

Your absolutely right, that check valve is the root of your problem.

You can take it apart, I'll bet you a dollar to a donut hole that it's chockablock full of sticky crap.

Clean it with a solvent (WD-40 might work), and it will probably reseat. Replacements are not all that expensive. A good tool house (contractor grade compressors) or a big truck store should have it.

As you have probably deducted by now, the blow down valve (the black valve close to the compressor that was blowing down the air) is doing exactly what it is supposed to do. It blows down the line when the compressor is "off", and the system depends entirel on the check valve at the top of the volume tank to avooid blowing down the entire system.

The "blowdown" is necessary to prevent the compressor from starting against a pressure head. Having to start against pressure would probably blow fuses. Make sure the electric solenoid valve is dumping the line from the compressor to the check valve, or you will develope compressor problems in short order.

As you have also probably deduced, the later 345's do not have electric valves operating the levelling system. It is done entirely by pneumatic valves mounted on each side of the tag axel.


Good Job!!

[swebster]

Oh sure - it make perfect sense now! I think Brett said in his first post - check valve. Then Jeff then zamboni. I even read another post by you stating the very same thing!

But did I listen and go there first? NOOOOOO. Instead I tore apart my air system and put it back together again!

I usually call this a "tail pipe inspection" when other people do it. I would joke that if a car stops running you don't run around the back and look up the tail pipe to see what's wrong.

Well - I'm getting better on this whole RV thing but I guess I have to understand it myself before I can fix it.

At least I know how the air system works. What did PeterH say about working on these old birds: "It's a state of mind"?

The good news is that my trip was postponed due to this ice storm so I have another couple of days to repair/replace the valve.

Thanks to all for the help and support (and patience). I'm hopeful I can WD-40 my way out of this one.

[87MH]

With a Light Bulb

Deep Dark Depression, Sordid Misery!!

We've all been there!

That's why we have each other -- and no life.

[Jim Tyrney]

Steven,
I am printing off this post for future reference and putting in binder. How much trouble would it be after you have gone thru your 86 345 MH air system to draw out a schematic of the lines, compressor, check, accumulator, etc. and post? Unless there is a schematic that already exists!!! Thanks, Jim

[RivetED]

Big trucks (Freightliner, Peterbuilt, K/W, etc.) use similar valves on their air systems, I'd try a truck parts vendor...

[ALANSD]

I got some parts from Grainger suppley for mine. They had most in stock and cheap.
My valves did clean up when I sprayed WD-40 through it also.

Now a question--since I have the manual input on my bags now, where would I put a gauge to check the air level?
Putting it after the valve wouldn't do it as the check valve is inline after that. I get a reading of zero at the input valve with the bags looking pretty full. I can live without the gauge but it would be nice to have one.
I am leaving the compressor out of the loop for now.
Too many other things to upgrade.

[swebster]

Alan,
I didn't think of Grainger. I'll try them too.

On your gauge. Mine has a line running out from the moisture tab (bottom of the accumulator tank) out to a bracket on the pass side frame right between the drive and tag axles. (It's easy on the 345 since the tank is located right there as well. It may be different on you 280)

It's terminated with a schrader valve so it's easy to blow out moisture and to take a reading whenever I check the tire pressures.

Seems like all you would need is a line of air hose, the right connectors, a schrader valve and and angle braket to mount something like this.