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Old 01-27-2004, 09:55 AM   #15
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does the guage your looking at indicate a change in air pressure??? sounds like you are venting air some where for some reason. that isnt much help but if the compressor only comes on when you start the coach i wouldnt worry about it.
as brett suggested look at the bags and see if they are in good shape . on my tank i have a shrader valve check the pressure there and wait a day and check it again . then you will know for sure it is venting . most cases it is venting thru the compressor as the check valve is stuck partially open
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Old 01-27-2004, 11:02 AM   #16
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Update

I just got off the phone with Phred Sez and he tells me that Brakes are Air over hydraulic and that is why the compressor fires up, to pressurize braking system.

Compressor should run on initial startup.

Thanks Phred,
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Old 01-27-2004, 12:21 PM   #17
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I would double check on that. I can't imagine a manufacturer using a 12v compressor as part of a braking system. I have also never seen an air over hydraulic on a p32.

Look at your PS pump. Does it have lines going to the master cylinder? If so it is a hydoboost and not air over hydraulic.

John
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Old 01-27-2004, 12:32 PM   #18
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Ken,

Fred's MH is a diesel pusher, he has an air over hydraulic system. I don't think that the p-30 series chassis came with that type of setup. Normally it is a hydro boost like John mentioned above.

If you are using the jacks to level the coach you could be causing the leak down. On mine if I use my stabilizer jacks and lift the coach to finish leveling (they are 5K rated screw jacks) I will dump some air. Then when I set it down the rear will sit out of level until I power up the compressor and the bags refill.

There may also be a section of the system that does not maintain the 120 PSI. This is normally to prevent the compressor from having to start against a high head pressure situation.

All in all I think you have a small leak. I would start at the bags themselves and check condition, then look at leak testing all of the fittings. One other option is to set the jacks, leave it for 5-7 days and see what bags(s) are soft. Then troubleshoot toward the compressor from there.

Most of the OEM compressors are rated for 20-30% duty cycle, so even if you continue to use the coach you should not cause additional harm to the components, I would be more concerned for a failure of some sort while on a trip. If it was a bag, it took me 3 months to get mine
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Old 01-27-2004, 12:46 PM   #19
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Level

During lunch break I went over and looked at MH.
The unit sits almost 2 inches lower on driver side than the passenger side.

The bags appear to be in good condition but I did not get real good look all over the bag.

The shocks seem to be the same on each side.
The axle arm is practically level on each side, (neutral),

I cannot see a broken leaf spring but I did not get a good look.

As for Master cylinder, I know that there are directions for bleeding both master cylinder and steering pump. I know that the brakes are dependant on the belt system. I know this because when I had to stand on the brakes on the way home from Houston, the belts went to squeeling loudly.

Brett, I have not deployed jacks so I dont think that is a factor.

The leaf springs are adjustable on each side. There are three holes in the bracket. Each side is bolted to the lower most hole. Same on each side.

Tomorrow, I will take photos of everything and post for the gallery.

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Old 01-27-2004, 01:34 PM   #20
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Air, Brakes, and Scratching my Bald Head

I have to agree with John and Brett, the brakes are power steering pump assisted. I ran down to PPL at lunch and looked at a '92 on their lot, there was no mention of air over hydraulics in the '92 Chevy Chassis Service manual. It only mentioned vaccuum and steering hydraulic assist power units. Sweet use of space under the front hood.

Now, the '92 was squatted way low in the rear, way to low to be out on the road, so Ken's "low rider" may be endimic to the G2.

I would be concerned about a 2" lean to one side. Could be the bag, could be something else. My air beam is also mounted in the lowermost of the 3 holes in the spring/beam interconnect bracket.

I'd still highly recommend weighing the 3 axels - that will give you a starting point for mods and weights and balance. If you could weigh each side of each of the three axels, that would confirm or disprove that the lean is caused by too much weight on one side of the MH.

Ken, do you have an air pressure gauge mounted in the dash panel?
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Old 01-27-2004, 01:38 PM   #21
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Pressure guage

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.

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Old 01-27-2004, 01:49 PM   #22
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Air Pressure Guage

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.
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Old 01-27-2004, 01:54 PM   #23
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System pressure

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?

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Old 01-27-2004, 02:04 PM   #24
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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?
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Old 01-27-2004, 02:10 PM   #25
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.....I would assume you have 4 valves.

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.
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Old 01-27-2004, 02:11 PM   #26
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Brett

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!

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Old 01-27-2004, 02:24 PM   #27
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One sensor controls one airbag.

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.
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Old 01-27-2004, 02:28 PM   #28
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Re: Brett

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.
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