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Old 11-15-2016, 06:57 PM   #1
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Low Air Pressure Indicator Alarm

Folks. Luckily I haven't had to post in awhile but I DO own an RV!!! I have a 2008 Fleetwood Expedition with a Freightliner chassis diesel pusher 38F with a Cummins engine. I'm cruising down the road and both 1 and 2 air brake dials show roughly 120 PSI but yet this alarm continues to sound.

At first the alarm in the dashboard would go off an on intermittently but now it stays on for miles. I've tried hitting the brakes, pulling off and shutting everything down but have also noticed that sometimes if I hit a bump or several it will stop.

I've read a few folks saying it might actually be part of the parking brake alarm and may need to be looked at or clean contacts. Don't know where to start with this one. Would like some thoughts and some pictures maybe of what to look for as it looks as though the air braking system is not for the faint of heart! Thx in advance.
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Old 11-15-2016, 07:25 PM   #2
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Mine will do the same thing intermittently. If there is no light or low gauge warning then it is as mine is the parking brake warning.. mine will either go off while driving or just when the brake is released in gear and won't stop for a few miles. It's annoying and I do have to do something about it.
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Old 11-16-2016, 05:43 AM   #3
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I get the light and the annoying alarm even though I have 120 psi on both gauges. Thinking that the gauges might be stuck I even cycled the gauges using the instrument test.
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Old 11-16-2016, 05:57 AM   #4
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Does your coach have hydraulic or electric stabilizer jacks? If hydraulic jacks, then my best guess to the alarm going off and then on would be the jacks or stabilizers are a little bit low on fluid. Easy to fix. Just let me know.
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Old 11-16-2016, 06:41 AM   #5
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Contact Freightliner with chassis serial number. I had a similar problem, Freightliner sent me new wiring harness that went in the dash, I had them installed several years ago. Solved my problem. I have a 2007 coach on Freightliner chassis.
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Old 11-16-2016, 07:13 AM   #6
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The first problem is to determine what that alarm represents. Even though in the dash, it may have triggers other than the air system. Other things that could be wired to the alarm include jacks-down, tv antenna up, etc. Any of them could be real or a false alarm.

If it is air-related, it could still be a false alarm. Ask Freightliner Custom Chassis Customer Service (1-800-FTL-HELP) where low air is sensed (I think it is at the gauges) and how to verify whether it is working or not.
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Old 11-16-2016, 07:34 AM   #7
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Great input everyone, thanks so much! Watched a couple of video's on how all the air brake system works and it seems like it could be a host of things.

I have the automatic electric jack leveling from Power Gear so that might be off the list, however, we have noticed the last week that the driver side front jack seems to dip over a day or two. All four jacks are less than 2 years old!

I'll give Freightliner a call to see if they can't rule out a few things.

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Old 11-16-2016, 08:01 AM   #8
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We had a 2008 Tiffin Allegro Bus with similar problems and I finally fixed it. All dash gauges and the low air warning run off the multiplexed data bus from the ECM. This means that all these gauges are daisy chained on the same wires. Each gauge and warning picks the info it needs for it's display off the data stream and ignores the rest of the stream. I dropped the dash and pulled all the jumpers and data feed lines off the back of the gauges and then reinstalled all the jumpers and plugs to different places. My problem never occurred again. A cheap and easy fix to try before you have to get more thoroughly involved.
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Old 11-16-2016, 02:09 PM   #9
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Thanks for the info folks!! Just got off the phone with Freightliner folks.. they were great to deal with.

He had me expose the dash and look to see if the interconnect cables between the gauges were white or black... Guess it's a known issue with the white wire bundle as some of you pointed out in the discussions

He's shipping the harness to Tampa so I can change it out. I will provide the harness number as well as an update to if it fixes the issue when I get a chance.

Thanks for everyone's help as always!!

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