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Old 07-30-2004, 08:06 PM   #1
Rivet Master
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Chesapeake , Virginia
Join Date: Jul 2004
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Air Bag Pressure Checking and Adjustment

Another question on the '89 370 I'm looking to buy: When I drove it to my house for the "try out" run, it seemed to ride extremely hard. I've adjusted the tire pressure as per the manual (70 psi front, 60 psi rear), and that helped, but I don't see in the manual how to check or adjust the pressure in the air suspension. I'm sure I'm missing something, but this thing's so complex compared to my travel trailer it gets a little overwhelming. Can someone tell me how to check the bags, where they're checked, how to change the pressure, and what the pressure should be? Is the whole system interconnected, or is each bag a separate pressure? I'm assuming this info is in the manual, but I can't find it. Greatly appreciate any help with this.

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Old 07-30-2004, 08:38 PM   #2
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1986 34.5' Airstream 345
Louisville , Kentucky
Join Date: Feb 2003
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OK, from here on out please understand that there are likely to be differences between the Gillig and P30 Chassis. I'll tell you how thing work on mine (on a P30) and there may be similar systems on your as AS added many things during the coach construction but you're kind of on a "try it and see" until you get a feel for this coach.

The 345's use a compressor, and accumulator tank and leveling valves attached to the tag axles to manage air pressure (and height) in the bags and air pressure transferring between the bags (like in a turn).

On mine the compressor (located under the bed curbside) turns on with the ignition if the pressure is below 100 psi. There is a high limit switch which turns it off once it hits pressure. Lines are plumed into the accumlator tank (between the tags mounted up under the frame). Mine has an additional PO added on/off switch and pressure gauge up front. The correct bag height on the P30 is 10 1/2 inches. Too little and you can damage things.

I have no idea what your Gillig setup could be. My advice would be to get under there and see what you have, what works, where things are located and take a manual pressure reading on the bags. You do not want to drive at speed without air in these bags as you could damage the chassis and/or the tag axles.

Also - do a search on the forum for air compressor, air bags, bag height, etc. You will find many many posts and a lot of good information from others who have been here before
Steven Webster
1986 Airstream 345 Classic Motorhome
AIR 1760
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Old 07-30-2004, 09:17 PM   #3
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1978 31' Sovereign
Texas Airstream Harbor , Zavalla, in the Deep East Texas Piney Woods on Lake Sam Rayburn
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Air Bag Pressure


Steven did a very good job describing the rear air suspension. Remember that the rear suspension is "automatic", and is set by adjustments for each air bag. The adjustments are set at the factory, and should not be changed unless you know for sure they need changing.

Steven did not mention the front airbags. Please remember that both Steven's and my Motor Homes are on the Chevy chassis - but there is a good chance that the Ford Gillig is similar.

The front Airbags should be at 60 psi. The front airbags are a "maintenance" item. Usually, they either hold pressure and are OK, or they don't hold pressure and must be replaced, unless there is a leak in the line, there is not much that needs to be done, other than to check the pressure from time to time. There should be one or two valves somewhere in the area of the front lights or bumper that look just like tire valves. Follow the line that leaves from the valves, and they should lead to the bottom of the front air bags.

The front airbags may or may not be joined together to a common fill point, it really does not make much difference.

There are several threads here on replacing the front air bags. Some have stated that for what an RV mechanic charges for replacing them they would not attempt to replace the bags themselves. Bags are available at places such as Camping World for less than $100 per pair.

"Suck it up, spend the bucks, do it right the first time."

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