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Tag axle air bags do not inflate


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I've been having an issue for some time now that the 2 air bags for the tag axle are not inflating when I start the coach and there is no air in the system.  The front and drive axle air bags inflate fine, the only way I can get the tag air bags to inflate is if I manually add air to the rear air bags using the control panel, then when I turn the system off, it will let the appropriate amount of air out to level for travel.

What I'm wondering is how valves are distributed for the air bags, is there a valve for the tag axle bags only and the drive has it's own valves as well? Basically, I'm looking for a bit of an explanation on how air bags are filled in the rear.


Mike B

01 Dynasty with Tag

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I'll assume you have a HWH air leveling system.  If that's true, when in level or manual mode, the two tag air bags on the tag are split with the tag airbag on the DS tied to the 2 DS drive airbags. Ditto on the PS.

When in travel mode, the tag axles air bags are tied together and controlled by a pressure regulator in the engine bay.

There are a series of air valves above the drive axle that control air suspension based on whether you are in travel, level or manual mode.

Here is a link to our files where you should find more details on your air suspension system.


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7 minutes ago, obb_taurus said:

Sorry Frank,

Yes, it is an HWH system.

Thanks for the link.

After your explanation, I'm still puzzled as to why it's just the tag axle air bags which don't fill in travel or level mode yet they fill in manual mode.


A failed pressure regulator in the engine bay that feeds air to the trag airbags in travel mode could be the problem.  Also, the air control valving could be defective.  Start first with the pressure regulator to rule it out.  Then it's a valving problem and the service manuals should help you out.  Also, double check that you have a good connection to the dash HWH control panel.

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1 minute ago, obb_taurus said:

Thanks Frank, will try replacing the regulator if I can find one, I live in Canada and it seems like whenever I try to find a part, it's darn near impossible.


First look at the regulator gauge and see if it's set to about 40 psi in travel mode.  If it is, you can test the regulator by setting the pressure to zero than removing the outlet line than dial up pressure to see if air comes out.  If it does, likely the regulator is fine.

If you haven't checked make sure you have a solid electrical connection to the bottom of the control panel.

If all that checks out, follow the manual troubleshooting to identify which valves are likely the culprit.

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The regulator gauge is sitting at about 50psi.  I was going to try what you suggested but was unsure which side was the outlet, my guess was the side with the black hose although I wasn't going to try and remove it because the connectors are threaded right into the regulator and I'm not even sure how to get the lines off cause I can't turn the lines, so I'm not sure how to remove the line.

The control panel seems to be functioning with no problem, I had an issue where the ribbon cable fell off but I took measures to ensure it doesn't fall off again.

Will include a photo of the regulator, perhaps you have some suggestions on how to remove the connectors and if my assumption about the black hose being the outlet is correct.



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Those are push to connect air fittings.  You first dump the air then, in your case, push up on the ring where the air hose goes in and this will release the air hose so it easily comes out.  But for this to work there can be no air pressure on the line.  Some times you have to give it a tap using and open end wrench next to that ring.  Since you are seeing normal air pressure on the regulator, it's unlikely that the regulator is bad but worth checking before getting into troubleshooting the valve manifold.  If you get to the point of working on the valve manifold, be sure to have the coach properly supported and all air dumped out of the airbags and tanks before you get under the coach to work on the manifold valving system.

The link to the manuals should help guide you through the valve manifold troubleshooting steps.

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11 hours ago, 96 EVO said:

Does the pressure on your regulator gauge drop to zero when you press tag raise button?

Tried this out and the gauge stayed at the same reading, ~50psi when the tag axle was lifted.  I did however eliminate the regulator as the issue, I pulled off the line from the outlet and air comes out of the regulator. 

Guess this brings me back to either the manifold or the control box.

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