Air brake gauges

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7258shane11

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Oct 13, 2009
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My air brake gauges are jumping up and down. Sometimes one does then both do and all the time the buzzer is active. Any ideas what would cause this.
 
Hi 7258 and welcome to RV Forum...

Electrical problems, often a bad ground for the dash instruments, is often the cause.  On the Freightliner chassis, there is a component called the VDO that can cause this sort of problem on some of the dash gauges, but I don't think the air gauges are driven by the VDO.
 
7258shane11 said:
My air brake gauges are jumping up and down. Sometimes one does then both do and all the time the buzzer is active. Any ideas what would cause this.
Click to expand...
What chassis do you have?  Freightliner had some problems with the VDU/VDC a few years ago.  There is a fix for it if that is what you have.   Please tell us what chassis, year and more details of the "jumping" around if you can.

TIA,
 
What kind of chassis? What about the other guages? Are they normal when the air guages act up? Do you get a "see info center" fault? Is the buzz the same as low air? My Freightliner/Cat gives a different type of "buzz" for low air vs. other faults.
"Bouncing" guages sounds like electrical. From what i can see of mine both air pressure sending units feed to a driver that in turn sends info to the guages. A fault on either side will activate the buzzer.
Another question: the "driver" seems to tell the compressor to either run or not run. What does your air comp do when the fault occurs??
 
RV Roamer said:
Hi 7258 and welcome to RV Forum...

Electrical problems, often a bad ground for the dash instruments, is often the cause.  On the Freightliner chassis, there is a component called the VDO that can cause this sort of problem on some of the dash gauges, but I don't think the air gauges are driven by the VDO.
Click to expand...

Gary,

In the FL VDO, there are 2 pressure transducers for the front and rear braking circuits.  In certain ones around 1999 to at least early 2002 chassis there have been numerous problems with their mounting and cracked solder joints.  I believe my write up for fixing the VDC is on the diesel rv and possibly the FCOC lists.  I know it is on the Newmar owners one.
 
Jim,
Thanks for the info on the VDO pressure transducers. I've seen two different reports about pressure gauges and the FL VDO. Wonder if there might be two different designs? I've never looked for mine - it's buried somewhere in the rats nest of dashboard wiring.
 
Thanks all for the wellcome. It is a 2007 Coachman Pathfinder 40' on a freightliner chassis. Answer to some Questions, all the other gauges work fine. I will have to check and see if the comp. is active while the gauges are bouncing. A light does come on in the dash while buzzing. I just assumed it was for low air warning will check. As for more details. It could happen 10 minits into a drive or 1 hour, but once it start bouncing it might bounce for 10 minits then stop for 1 minute and so on. The gauge go from full to zero within 1 second then they might go to 50 pounds then back to full or then again they might stay on zero for a minute than jump back up. so on and so forth.

thanks
 
7258shane11 said:
My air brake gauges are jumping up and down. Sometimes one does then both do and all the time the buzzer is active. Any ideas what would cause this.
Click to expand...
Thanks all for the wellcome. It is a 2007 Coachman Pathfinder 40' on a freightliner chassis. Answer to some Questions, all the other gauges work fine. I will have to check and see if the comp. is active while the gauges are bouncing. A light does come on in the dash while buzzing. I just assumed it was for low air warning will check. As for more details. It could happen 10 minits into a drive or 1 hour, but once it start bouncing it might bounce for 10 minits then stop for 1 minute and so on. The gauge go from full to zero within 1 second then they might go to 50 pounds then back to full or then again they might stay on zero for a minute than jump back up. so on and so forth.

thanks
 
With a 2007 chassis you should still be under the FL warranty.  I suggest you take it in. 

Your symptoms sound like the classic display unit problem with the pressure sensors.  If you are not under warranty I can send you the instructions on how to fix but you must know how to solder and be electrostatic aware to ensure that more damage is not caused as the display unit is about $500.
 
i have the same problem with my air gauges, they keep sweeping back and forth and my buzzer stays on. i own a 2001 dutchstar with a freightliner chassis. does anyone know what the fix is or was?
 
Kfirth,

The fix was and is to take a box out of the MH, open it up and do some soldering.  I wrote a "how to do this", "Repair FL VDU.doc", see here  and it is posted in the Yahoo Newmar owners group,
http://groups.yahoo.com/group/newmarowners/ and also the Freightliner Chassis owners group, http://groups.yahoo.com/group/FCOC/.

If you have any questons, contact me via ac7po at bresnan dot net.
Edit: Replaced long URL and horizontal scroll.
 
thank you very much jim i will check that out in the shop here and reply to what i found, im brand new to the forum and liscensed tech in automotive and heavy duty trades so i will help out as much as i can also, thanks again and i will post soon
 
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