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Old 09-20-2021, 06:54 PM   #1
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Rear air tank pressure issue

2003 Winnebago 34 with a cat 330 on a freightliner chassis. ONLY when atraveling down the road the rear air dash gauge will drop from 130 to 100 in about 5 minutes, then re-charge to 130, constantly. Front tank stays at 130. When parked with air brake on or off, stays at 130. I have crawled from one end to the other trying to find an air leak and can't hear anything. had 2 new rear air bags installed recently, and thought that might stop the cycling, but still does it. Anyone have ideas on anything to check that might use rear air when moving? Ride height sensor? Never had a braking issue, but it is bugging me. TIA
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Old 09-20-2021, 07:24 PM   #2
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When did you last service the air dryer? That sounds like an air dryer that is not working properly.
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Old 09-20-2021, 07:31 PM   #3
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Had a full service done at Freightliner Gaffney SC 2 months ago, new air dryer then, along with new rear airbags.
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Old 09-20-2021, 11:11 PM   #4
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You'll need and air system diagram from Freightliner linked to your chassis serial number .
To see if anything other that the rear brakes are serviced with air from the rear tank ,
Freightliner Free Help line.
1-800-385-4357 have your serial number handy , it's the first thing they ask for.
My 99 chassis the whole air suspension system , the air horn , and the activation air for the exhaust brake all come from the front tank. So when driving my front air gauge fluctuates; as the ride height valves compensate for chassis lean in corners and the exhaust brake is used.

Your 2003 motor home could be on a 2002 Freightliner chassis , the 2002 chassis have known issues with air gauges; but the issue is usually a sudden loss of reading and a low air light & warning buzzer.
Look for a Freightliner data decal , low on the wall to the drivers left , for the chassis build date , or ask Freightliner for the date when you call .
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Old 09-20-2021, 11:44 PM   #5
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The air suspension is always actively adjusting while running down the road.

The ride height valves can move about a 1 inch with no air use but with anything more then that they will inflate or deflate the airbags.

Any undulations, curves or leaning in the road surface will cause the valves to adjust , using small amounts of air.
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Old 09-21-2021, 06:47 AM   #6
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Our coach is a 2002 production year, and has had the air gauge issue happen and faulty unit replaced. Does the ride gauge control air bags in front and rear? or only in rear? Is there seperate ride gauges for front and rear? Coach is headed to FL Gaffney on Friday for a different issue. Wanted to be informed before asking them about possibilities.
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Old 09-22-2021, 07:58 AM   #7
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Quote:
Originally Posted by rebrobin View Post
Our coach is a 2002 production year, and has had the air gauge issue happen and faulty unit replaced. Does the ride gauge control air bags in front and rear? or only in rear? Is there seperate ride gauges for front and rear? Coach is headed to FL Gaffney on Friday for a different issue. Wanted to be informed before asking them about possibilities.
Part of the reason I say you need an air system diagram , linked to your serial number , is the over the years Freightliner has changed the air suspension system , my 99 chassis has 3 ride height control valves ; 2 front , 1 rear ; other members report , 1 front and 2 rear . I believe one year had 4 ride height valves.
But as I mentioned , my chassis air suspension , draws all it's pressure from the front tank, so the front tank gauge is the one that moves while I'm cruising .

As CaptBill has mentioned , I typed in the Freightliner phone number wrong.

1-800-385-4357 is the correct number

EDIT: A second thought , I always have them .
Your VDC was replaced , and movement in the front tank gauge is normal due to air suspension using air . ( exhaust brake , air horn )
Our electronic gauges respond to an individual signal , from the VDC, that signal could be incorrect , for the front and rear gauges , IF the front & rear air system lines; that provide the tank pressure to the sensors ; were swapped when the VDC was installed .
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