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smily · 01-27-2004, 12:38 PM

Yes I have air pressure guage in dash.
At least I think it is an air guage.
It actually indicates the state of Air Supension .
It has scale and graph lines as in green and red indication lines.

Smily

87MH · 01-27-2004, 12:49 PM

The reason I asked was that the '92 I was in at PPL today had a 0 to 150 psi guage mounted in the lower right hand corner of the dash. It was not marked as to just what it was measuring, though. Could be volume tank pressure, could be airbag pressure. I still had that in mind when the question of an air over hydraulics brake system was put to rest.

The identification of what the gauge is measuring would make a difference in troubleshooting your suspected bag problem. If you think your pressure indicator is for the bags, and you do not get an indication of the bags bleeding off, I would recommend confirming that pressure is in the bag by "feeling" (you'll know right away the difference between a pressurized bag and a deflated bag), and moving on to the next possible cause of your squat and lean.

smily · 01-27-2004, 12:54 PM

I was under the impression that the guage was indicating pressure over the whole system. Is the system not balanced or common to everything it is connected too?

Or are there different levels of pressure throughout the system. If so, how is that done, with regulators or something like that?

Smily

thenewkid64 · 01-27-2004, 01:04 PM

Ken,

I do not know for sure but I would guess that the dash mounted gauge is showing the pressure common in the system.

The bags may have a differing level of PSI in them. This is done by the leveling valves. They only allow enough pressure into the bag to raise the chassis to the cut off point. If it needs all 120 PSI to do it, fine. If only 80 PSI is needed then the valve cuts off the air. Some MH's have a valve for each bag, others have a valve for each axle. In your case it is important to determine how many valves you have to properly troubleshoot the issue. Based on Dennis's chassis ( the same one your rig is on) I would assume you have 4 valves. this allows for a better side to side leveling capability since the bags can be inflated and deflated independently.

The dash gauge is a telltale to let you know the condition of the air suspension. don't worry the frame whacking the axle will let you know if the bags are flat! The gauge can tell you if you are having a problem, or at the least if the system is working. Does the gauge sit lower before key on?

87MH · 01-27-2004, 01:10 PM

There's that word again.

Wrong.

Only two levelling/sensor valves, one mounted close each of the tag axel wheels, each one controlling one of the two airbags to the main axel.

The front airbags do not have a sensor, just Schrader valves for independant manual fill.

smily · 01-27-2004, 01:11 PM

If I understand what you are saying, it seems that you are implying that each bag can be independantly adjusted.
If that is the case, what is the Air Suspension systems for?

By comparison, the forward Airbags can only be inflated manually. They each have a seperate fill hose and valve that is mounted in the wheel well.

Are you saying that the rear bags can be the same as the front and they have to be filled manually? That would be good if that is the case. I would simply fill bags to specs and be done. But I cant help but think the Air Suspension is supposed to maintain the Air bags in the rear.

I will get to the bottom of this one way or another!

Smily

87MH · 01-27-2004, 01:24 PM

Ken:

Referring to the picture of the bare frame I posted earlier, the sensor next to the right tag axel wheel controls the right airbag under the main axel. The control sensor next to the left tag axel wheel controls the left airbag under the main axel.

They have independant controls (the sensors mounted next to the tag axel wheels) so that if a lot of weight is put on one side or the other, they will compensate to a certain extent.

thenewkid64 · 01-27-2004, 01:28 PM

Quote:

Originally posted by smily
If I understand what you are saying, it seems that you are implying that each bag can be independantly adjusted.
If that is the case, what is the Air Suspension systems for?

By comparison, the forward Airbags can only be inflated manually. They each have a seperate fill hose and valve that is mounted in the wheel well.

Ken,

The bags in the rear are maintained by the compressor and the leveling valves. This is automatic and the air in the bags changes as the load of the MH changes. The bags may have differing amounts of air pressure to do the lifting required at any point and time. This is the way that the airbag rear suspension is supposed to work. The main ones actually support the MH. The tag ones (If you have them) help the torsion axle support the MH.

The front bags are a completely different issue. These are set to 55 PSI and should be maintained there. They act as a damper and a support to help the coil springs so the front is not so boundy.

87MH · 01-27-2004, 01:33 PM

Brett:

I do not think that any AS tag axel has an air bag assist. As far as I know, all of the tag axels are straight rubber/torque tube supported - just like the trailers.

On Edit --
AS did mount the sensors for the main air bags on the tag axel wheel brackets, as the tag axel angle was an independant point of reference for the height of the bottom of the coach from the ground

Sorry if I inferred differently previously.

thenewkid64 · 01-27-2004, 01:48 PM

Dennis,

I was unsure if there were tag bags...........sorry I couldn't help myself.

I did not see then in your picture, but they could have been buried under the frame.

The mounting of the leveling valves makes sense on the tag axle. This assures that the tag axle is carrying a consistent weight and the tag axle capacity is not exceeded for a long period of time, leading to torsion failure.

On edit......

Ken the compressor should come on at start even if you are level if you have done one of the following. Filled the fuel tank, filled the water tank, filled the black water/gray water and not dumped, invited your whole family to go for a beer run, loaded up for a weekend and taken everything that will fit along, finished installing the new interior, etc.

After you dump, burn off a bunch of fuel, empty the trash, or tell the extra passengers to get out and walk, the system will automatically dump air to bring the proper weight back onto the rear bags and torsion axle.

donnall · 01-27-2004, 02:28 PM

I had the very same problem on my 33' LY.

My problem - and likely yours too - is that there's an sensor arm underthere that tells the pump when the rear is low and for the pumps to pump up the air bags.

A little bolt came loose from the arm and therefore the pump didn't know it was sitting low. The pump was fine, the airbags fine, they just didn't know they needed more air. It could very well be that one airbag has leaked down just a little faster than the other, causing your rig to set low on one side.

The shop put on a new nuts and it pumped right up nice and level.

I wish I could tell you exactly where the arm is located, I just know it's kinda hard to see, and located where it can sense the rear end hight.

The good news is it's a quick & easy fix.
Put on two nuts this time and lock them in place.

HTH
Don

smily · 01-27-2004, 04:34 PM

I walked in the house, gave a cursory peck on the wifes cheek and walked straight to the owners manual that is sitting on Kitchen table.
She asks "what are you doing"?
I mumble "trying to figure out why our MH sags".

Okay here it is.
Upon shutting down engine and MH, the solenoid to compressor opens contacts to allow compressor to bleed pressure off.

Reason: to prevent starting under high pressure next time.

So, a little pressure bleed off is normal, compressor will energize upon startup next time to re-pressurize.

But my compressor runs for three to four minutes, much longer than needed to rebuild minimum pressure loss.

So next logical thought: Why so much pressure to be regained? maybe tank is bleeding down through compressor as stated by Brett earlier....Why?
Because Check valve between compressor and tank is probably bad.

So that is my theory on cmpressor starting up on ignition.

Now, sagging rear driver side. I agree that it sounds like the sensor switch is not talking to system and not filling bag as needed. Probably due to loose bolts as pointed out by Donnall.

I will be checking state of sensor and report back.

Thanks for hanging in there with me today.

Smily

fangthorpe · 01-27-2004, 06:09 PM

When I picked up my '92 30' single axle, the VDO air gauge on the dash read 60#s and the coach rear was too low. The PO removed the stock springs and bags and installed Supercoils, which don't use airbags, so all gauge and compressor action is now limited to the rear bags. I crawled under the coach and adjusted the leveling valve arm (only 1 in center) about 1/4" and the compressor went on, raised the rear up about 2", and the pressure gauge now always reads 90#s. After 3 or 4 days, it will bleed off enough air to kick the compressor on when you hit the ignition, taking maybe 1-2 mins to pump up. Before I raised the ass level, it would always bleed off air when leveling, as the compressor wanted the rear lower than the front and the levellers wanted everything level. Unless something is preventing air from getting to the left bag or unless you have 2 leveling valves, I can't imagine why you have a sag on one side. Is there any chance the PO unhooked the rear bags when he unhooked the front ones, and you need to also air them seperately? Maybe the compressor is only filling the tank and not the bags. 120#s is too much pressure to have a sag. I'll bet the driver's bag is low.

smily · 01-27-2004, 06:49 PM

Book, (Service manual) says that I have two leveling valves. One on each side.
The forward bags were never attached to air system. They have always been independant. The book leads me to believe that air bags in the front were optional and not necessarily part of the original design. The book says that these are aftermarket bags and are not covered under warranty.

You maybe correct that no air is getting to back but I believe that the passenger side is getting air. The bag was very firm.

Tomorow, I will post scanned image of Air system. My money is n faulty leveler sensor on driver side.

Smily

swebster · 01-27-2004, 07:07 PM

Smily,
For what it is worth these guys (above) guided me through an issue with my air system recently. Turned out to be a bad check valve. I replaced it in five minutes with $10 in parts from Grainger.

I've not got into the leveling valves on my tags (yet). I replaced it to solve a different probem (full dump of air when I turned the ignition off) but noticed a small hairline crack in it once it was out. If would guess that this would be the reason for mine coming up to pressure much faster now.

smily · 01-27-2004, 07:20 PM

Then my guess was correct. If you read above, I speculate that my check valve is not working.
Did your compressor start every time you turned ignition on?
And run for several minutes?

swebster · 01-27-2004, 07:39 PM

Mine always come on when I start the coach. But now that I know the difference they used to take a long time to get up to pressure.

The Airstream manual says to expect it to come on when you first start the coach but mine would run a lot. My setup is a little different in that it appears as if my front bags are "plumbed" into the main air system. I had no idea anything was amiss until it started dumping all of the air when I turned it off.

smily · 01-28-2004, 08:14 AM

Anyone know the exact location of the two leveling valves on the LY? I am going to look today but I would like to minimize my search time. (crawling time)

Smily

swebster · 01-28-2004, 08:46 AM

Don't have a LY but if the P30 setup is the same and AS didn't change the component you should find them mounted inboard of each tag axle pivot just inboard of the rear shock mount. (You can see the mounting location in Dennis' picture above)

There are two air lines going into the back of the valve and a single open "blow out" line coming out. There is also a threaded rod down to the tag axle (this adjusts the valve position lever).

When I replaced my tag shocks this fall I removed the tag wheels and unbolted the leveler valve brakets to get at the shock bolts.

The valves were ready accessable with the tag wheel removed. Just remember to jack up the tag axle!

smily · 01-28-2004, 11:42 AM

I was typing just as site crashed.

I have had time to settle down.

I have been to unit and crawled under it. I have found where air lines leave tank and I have found dump lines. But for the life of me I cannot see the leveling valves. They are way up in the framework and I cannot get to them.

I will have to go back with flashlight and mirror I guess.

Obviously, it will not be easy to repair if needed.
I checked the bags again and they are like rocks. Do I need to raise unit to see bag collapse?

I am getting frustrated

Smily