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Old 01-10-2011, 04:21 PM   #1
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AS280 - Rear airbags bypassed

One more thread while I'm at it: Rear airbag system.

I recently had the rear airbags replaced because they had been completely 'popped' when I acquired her. The shop that did the work bypassed the tank/leveler system and simply connected the two airbags together with a hose to a compressor. Essentially, it is now as simple as could be. Manual inflation to whatever pressure you want. Over time they bleed down a bit (I suspect a leak in the line where the fitting meets the compressor). Then I pump them back up as needed. I was thinking about installing an electronic pressure switch that would trigger the compressor when the pressure dropped below 80psi and stop the compressor at 100psi. It's a simple $15 upgrade that would automate the whole system.

While this works just fine, I'm wondering why all that extra hardware was installed in the first place? Why include a storage tank? And, ultimately, should I (why would I) try to get the original setup working again?

/df
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Old 01-10-2011, 05:57 PM   #2
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One more thread while I'm at it: Rear airbag system.

I recently had the rear airbags replaced because they had been completely 'popped' when I acquired her. The shop that did the work bypassed the tank/leveler system and simply connected the two airbags together with a hose to a compressor. Essentially, it is now as simple as could be. Manual inflation to whatever pressure you want. Over time they bleed down a bit (I suspect a leak in the line where the fitting meets the compressor). Then I pump them back up as needed. I was thinking about installing an electronic pressure switch that would trigger the compressor when the pressure dropped below 80psi and stop the compressor at 100psi. It's a simple $15 upgrade that would automate the whole system.

While this works just fine, I'm wondering why all that extra hardware was installed in the first place? Why include a storage tank? And, ultimately, should I (why would I) try to get the original setup working again?

/df
The leveling valve was there to keep the system at the proper operating height. The correct height is 8 3/4" between the cross-members, air bag height. The valve automatically adjusts for changes in the weight of the coach, full vs. empty tanks, personal belongings and such. You can monitor pressure on a gauge but that won't tell you ride height as the load varies.

Adding a pressure switch to the compressor will vary the ride height by quite a bit because of the difference in the start/stop pressure. By the way the original system already had a pressure switch to operate the compressor. There should also be a check valve so that the compressor starts in a no-load situation.

The tank provides a reservoir so that the compressor doesn't have to cycle as frequently. It also provides a place for the moisture to separate so that it can be drained from the system.

The original design is a very simple, dependable, reliable system that is used everywhere in the trucking and luxury motorhome industries. You have created a manual system that will suspend the rear of the coach but not as well as it should.

The step can be replaced with an electric step for around $300-$400. My vacuum step works fine. I guess the need for an automatic step may depend on how long your legs are.

Cheers, Dan
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Old 01-10-2011, 10:03 PM   #3
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Air

[QUOTE=Smartstream;936349]

The original design is a very simple, dependable, reliable system that is used everywhere in the trucking and luxury motorhome industries. You have created a manual system that will suspend the rear of the coach but not as well as it should.


Cheers, Dan[/QUOTE]

I second that.

There are changes that can be made for improvement to some systems, but the air suspension is probably the simplest system on the unit, and if understood and maintained, will function a long time and will not create problems elsewhere. (eg. tire overloading- tag axle application, excessive rear wander, and steering problems because of improper level.) Also, the shocks are designed for each application as specified by the OEM and may not work properly if the suspension is not to factory height.

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Old 01-11-2011, 12:46 AM   #4
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I'm convinced.

Thanks to both of you. Excellent advice. Now it's off to find a reliable, honest and affordable P30 chassis shop around LA. Any suggestions there?
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Old 01-11-2011, 01:45 AM   #5
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I'm convinced.

Thanks to both of you. Excellent advice. Now it's off to find a reliable, honest and affordable P30 chassis shop around LA. Any suggestions there?
The manufacturer of our air suspension click is not far from you in Fresno. Also the leveling valve and fittings can be bought at any truck supply and you can install yourself, it's really pretty simple. The only tough thing might be the small air tank. There are tanks available but to find one to fit in the original spot might not be as easy. The thing is you can use any tank that you can find a place to mount and run an air line to it.

It has been 12 years since I lived in L.A. so I really don't know who is competent now but C&G Trailer is East on the 91 in Bellflower and if you keep going Andy at Inland RV is in Corona. Both are Airstream shops and should be able to help you.

If you have questions or need more details, just ask.

Good luck, Dan
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Old 01-11-2011, 11:08 AM   #6
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Get yourself an Aluminum Air tank made for all the baggers and lowriders... I just looked on Ebay and a 8 gallon is under $100, and a ton of shapes and capacities. Find a good shop locally that could do the donkey work... seems that there should be a load of them given where we live!
Lets face it, its not a lot different!
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Old 01-11-2011, 11:38 AM   #7
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Get yourself an Aluminum Air tank made for all the baggers and lowriders... I just looked on Ebay and a 8 gallon is under $100, and a ton of shapes and capacities. Find a good shop locally that could do the donkey work... seems that there should be a load of them given where we live!
Lets face it, its not a lot different!
That's the idea. On the 280 the original tank was about one gallon and sat vertically inside the rear storage compartment. That would be hard to find. Fortunately it doesn't have to mount there but it is convenient to drain the water every few days.

Cheers, Dan
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Old 01-11-2011, 12:07 PM   #8
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I would put a 6 or 8 gallon tank under somewhere and a Viair compressor feeding it. Then run a pipe to one of the compartments, and add a airline fitting. That way you have loads of air for the suspension AND capacity to inflate an airbed/tire or whatever. My 345 has an air fitting in the rear compartment.
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Old 01-11-2011, 12:28 PM   #9
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A great source for air tanks an pumps is www.hornblasters.com. While you are at it, add some train horns to your MH. I consider that the best upgrade I have done to mine

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Old 01-11-2011, 04:35 PM   #10
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Awesome suggestions. LOVE the train horns

BTW, mine already has a decent sized tank (est 5-10g) that is mounted underneath the coach where the leveling valves are. Appears to be stock. I know when I originally purchased this, there was a defunct compressor in the rear outside compartment (the AC hookup compartment). I've since removed that and have an aftermarket 12v compressor hooked up in it's place.

It seems it's just a matter of going through the system and doing some diagnosis to see which components need replacing.

Here's a question for you guys: I hear it's unsafe to work under a vehicle supported by airbags. And it's almost impossible to work under there when the bags are deflated. So how do you get some clearance? Do you use a jack and then place the frame on traditional supports? Seems even more dangerous...
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Old 01-11-2011, 06:06 PM   #11
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Awesome suggestions. LOVE the train horns

BTW, mine already has a decent sized tank (est 5-10g) that is mounted underneath the coach where the leveling valves are. Appears to be stock. I know when I originally purchased this, there was a defunct compressor in the rear outside compartment (the AC hookup compartment). I've since removed that and have an aftermarket 12v compressor hooked up in it's place.

It seems it's just a matter of going through the system and doing some diagnosis to see which components need replacing.

Here's a question for you guys: I hear it's unsafe to work under a vehicle supported by airbags. And it's almost impossible to work under there when the bags are deflated. So how do you get some clearance? Do you use a jack and then place the frame on traditional supports? Seems even more dangerous...
Post a few pictures of what you have. My coach only uses one leveling valve mounted on the front side of the upper cross member pretty close to the center. I'm curious about your tank because my 280 is pretty full around the area of the rear axle, air suspension and fuel tank.

When the air bags are deflated the coach actually sits on the leaf springs. Be careful where you jack up or set your jack stands as you will flex the frame and stress the body. The easiest way is to drive the coach up on 2, 3, or 4 layers of 2"x 8" wood. I cut them in 2', 4', 6' and 8' lengths and stack to form a ramp. Put jack stands under the rear axle or under the frame just behind the rear axle. This is where hydraulic leveling jacks would mount. I tried to set jack stands forward of the axle and it flexed so much you could barely open or close the door. I don't do that anymore.

Cheers, Dan
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Old 01-11-2011, 06:15 PM   #12
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Dig around here and get some ideas...
VIAIR Corporation - 12 & 24 Volt Air Compressors

Watch the video...
http://www.viaircorp.com/OffRoad/
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Old 01-11-2011, 07:07 PM   #13
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The original compressor was powered through the dash switch and a fuse in the firewall mounted fuse block, a real nightmare to change.

I installed a Viair 450C-G compressor, a great little pump. It has a 100% duty cycle at 100 psi. I set the pressure switch at 100 psi. and the air bags run about 72 psi. at design ride height. The pump power supply is through a relay and circuit breaker mounted near the batteries. The relay is controlled by the original dash switch. I haven't had any problems at all with this set up.

Cheers, Dan
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Old 01-16-2011, 07:44 PM   #14
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Post a few pictures of what you have. My coach only uses one leveling valve mounted on the front side of the upper cross member pretty close to the center. I'm curious about your tank because my 280 is pretty full around the area of the rear axle, air suspension and fuel tank.
Cheers, Dan
Had a great day under the 280. Took some pictures of my setup. The tank is forward of the rear axle and quite large--about 24" long by 10" in diameter. There are three connection points on the tank. You can see the attached pictures for details. I haven't thoroughly tracked each of the hoses, but it would appear this is an air tank, yes?

/df
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Old 01-16-2011, 07:46 PM   #15
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And just for more details, here are the three connection points on the tank:
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Old 01-16-2011, 07:51 PM   #16
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And finally, some photos of my rear axle setup. it looks to me as if an air hose has been cut, yes?
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Old 01-16-2011, 08:42 PM   #17
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Familiar territory. I had the same challenges. Here are a few pictures of our solution.

Vinnie
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Old 01-16-2011, 09:01 PM   #18
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Familiar territory. I had the same challenges. Here are a few pictures of our solution.

Vinnie
Nice work, Vin. I wondered how that was installed.
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Old 01-16-2011, 09:15 PM   #19
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that hose is not cut, it looks like the relaese side of the leveling actuator (to lower pressure). when working with 12 pumps, make sure they have some ventalation and decent wiring. the heads can get VERY HOT, especially on a 5+gallon tank and 1 compressor

i have a AZ comp in my truck for power tools, works really well.

::Welcome to Air Zenith::
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Old 01-16-2011, 10:48 PM   #20
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that hose is not cut, it looks like the relaese side of the leveling actuator (to lower pressure). when working with 12 pumps, make sure they have some ventalation and decent wiring. the heads can get VERY HOT, especially on a 5+gallon tank and 1 compressor

i have a AZ comp in my truck for power tools, works really well.

::Welcome to Air Zenith::
Great pictures. If you look at Airslides first picture that small black vertical tank to the left is what I have in my 280. There is a schrader valve on the bottom accessible under the coach to drain water. The original pump was powered through a fuse under the dash. Vinnie added the round relay at the rear of the compartment. I installed a similar one next to the batteries. You want a short run of heavy wires to power the compressor. You can also see the pressure switch.

Finch is correct that the cut tube is the valve exhaust that releases air when the ride height is too high. It looks like the tube to the rear of the valve goes to a tee to supply the bags and the last tube goes to the top of the tank. The other small tube on top of the tank probably goes to a gauge on the dash. The tube on the bottom of the tank could be the supply from the compressor and the larger diameter fitting could be a check valve. The other tube may go to a fitting somewhere to connect a hose to inflate tires and or supply air tools. Just a guess.

The air bags look way overinflated in the picture. The spool on the bottom of the bag should only have about half that much exposed. The dimension between the cross members, air bag height, should be 8 3/4". The hole in the valve arm is slotted and by loosening the bolt you can move the arm up or down for small adjustments. You can also bend the link that goes from the valve arm to the bottom cross member if you need to. If that is the original valve there is about a 15 second delay from the time the arm is moved until the air is charged to inflate the bags or released to deflate the bags. This prevents the valve from cycling every time you hit a bump or pothole and to prevent frequent compressor cycling.

Just out of curiosity what is in the white PVC conduit running under the frame rail?

Cheers, Dan
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