Air gauge

[Luckiest Dre]

I can not seem to get more than one trip behind me without one or both of the air gauges going bad. Yesterday the primary gauge started sending me the audible alarm telling me that I was out of or low on air pressure. When in fact what is happening is the gauge looses signal (or is just a poor design) and indicates loss of air pressure even though there is sufficient air available. After having replaced (under warranty) the gauges twice before, I am getting rather tired of it. Has anyone been having trouble with them as well? What I am really afraid of is at some time in the future it will cry wolf and I will ignore it only to really have a loss of air!
I have a 2008 Gulfstream with the Mercedes 900. The chassis is a 2006.

[Elkhartjim]

Larry, its not the gauges its probably the LBCU and/or the wiring harness. Call Freightliner Gaffney, they should be able to help you.

[Luckiest Dre]

Jim
Thank you for responding. The Local Freightliner dealer diagnosed the problem as the gauges, as did the dealers in Canada. I am hoping that your observation may be correct but do not know what Gaffney is. Do you have any contact info?

[Elkhartjim]

I had the same problem. Driving down the highway the gauge would drop to zero and the alarms would go off. Remember, if the air pressure actually goes to zero the brakes will lock and also for the pressure to go from 130 psi to zero instantly the end of the air tank would have to blow out. I had it in a couple FL shops and they thought it was the gauges. The problem, they have no clue what the light bar control unit (LBCU) is because its not in the dump truck next to your motorhome.

Freightliner Gaffney, SC is where the chassis is built. They have a 24/7 help line. 1-800-FTL-HELP.

One caveat, your Mercedes and I don't have a clue how that fits in the picture. Good luck. Oh, when you call FL you will need the last four digits of your VIN.

[goldwingerx2]

Larry, sorry to hear you are still having problems with the gauges. Hope you can get it fixed this time.

Dean

[smlranger]

Larry, Freightliner uses a VDU/VDC (vehicle data unit, vehicle data computer) that sends signals to the dash gauges. Some of the VDU's had defective (cold) solder joints on the circuit board where the air pressure transducers attach. If that is your problem, and you are good with a soldering iron, the VDU can be removed, opened, the joints re-soldered, and you may have a fix. A number of folks, myself included, had this problem and did the fix. My re-solder job lasted over 2 yrs before my VDU started acting up again. So, I replaced the VDU in October...it cost me about $350.

If your coach has the same issue, the folks at Freightliner can tell you based on your description of the problems you are having. Suggest you call the Freightliner help line and, if they tell you the VDU is the problem, send me a PM with you email address and I will send a detailed technical article on how to do the repair.

[Luckiest Dre]

Thanks all for your input!
My chassis is still under warranty with Freightliner so I should not need to do it myself. It seems that what I need is the right repair/DIAGNOSIS. I will call the help line and then suggest my dealer give some consideration to the suggestions I have received. I don't usually tell my DR. what or how to operate but only what the symtoms are. I have found that telling the mechanic how to turn the wrench usually costs me more. Yet when the same problem continues to resurface it is time to look beyond that normal circle!

[Luckiest Dre]

The mechanic at Freightliner called Gaffney as I suggested from the comments on this site. They determined that it was the Daisey chain or as i understand it the wiring harness that is the culprit. We are now waiting for the parts to come in from two different locations.

[Elkhartjim]

Quote:

Originally Posted by Luckiest Dre The mechanic at Freightliner called Gaffney as I suggested from the comments on this site. They determined that it was the Daisey chain or as i understand it the wiring harness that is the culprit. We are now waiting for the parts to come in from two different locations.

That was the first thing (wiring harness) they replaced on mine and when the problem continued they replaced the LBCU. I'm glad you convinced the dealer to call Gaffney.

[KennethM]

Luckiest DRE, ElkhartJim has the solution to your problelm and sounds like you are well on the way to fix. I have had both air gauges fail under warranty with actual air leaks and replaced them. The same problem as you described began on #2 gauge only which is the end of line on my system. Freightliner Help totally updated me on the LEN lines from the LBCU and the fact the gauges on our units have ID's and the wiring is actually a information buss. Information was the cure for my problem I wiggled the connector in and out of #2 gauge problem solved for 2 years now as a side note in my system had the problem been up stream on #1 then both gauges would have done as yoursl.

[J Walker]

I hope the harness fixes it but is suspect not. I don't know how they could have diagnosed it to narrow it down to the harness. I don't believe they have test equipment for that. Like others on this thread I had the problem you describe, drove it to Gaffney, described the symptoms, and they replaced the VDC. All of this without even a single test. Fixed the problem!

[Luckiest Dre]

Quote:

Originally Posted by J Walker I hope the harness fixes it but is suspect not. I don't know how they could have diagnosed it to narrow it down to the harness. I don't believe they have test equipment for that. Like others on this thread I had the problem you describe, drove it to Gaffney, described the symptoms, and they replaced the VDC. All of this without even a single test. Fixed the problem!

I suspect that I will have an answer by the time I reach Florida!

[Elkhartjim]

Quote:

Originally Posted by J Walker I hope the harness fixes it but is suspect not. I don't know how they could have diagnosed it to narrow it down to the harness. I don't believe they have test equipment for that. Like others on this thread I had the problem you describe, drove it to Gaffney, described the symptoms, and they replaced the VDC. All of this without even a single test. Fixed the problem!

The LBCU (Light Bar Control Unit) replaces the VDC in later model RV's.

[Thewellz]

Elkhart Jim "If the air pressure actually goes to zero the brakes will lock"
I believe the auxillary air tank will support the Primary tank in order for you to make an emergency brake application before your spring brakes "Lock", otherwise you could lose control if the brakes lock up at speed, you man test this by draining the wet and primary tanks and then by depressing the brakes with your wheels chocked and the spring in the release position, you should hear air moving to the rear brake pots from the auxillary tank.