Rear Air Alarm Today

[noserider]

Driving the RV today I got the low air light/buzzer and the rear air gauge went to zero. I pulled off the road. Front pressure was reading normal. Coach was functioning normal. No change in air suspension or braking. Was close to home so back on the road. When I was parking the alarm went off for a second and i noticed when this happened the gauge momentarily went to normal and then back to zero. I did not have time to troubleshoot but I did disconnect the connection to the gauge and reconnect a couple times with no success. Tomorrow I was thinking to switch the leads on the front and rear air gauges and see if I can make the front gauge work with the rear plug and see if the rear gauge will work with the front plug. What say you guys?

[DD788Snipe]

Originally Posted by noserider

Driving the RV today I got the low air light/buzzer and the rear air gauge went to zero. I pulled off the road. Front pressure was reading normal. Coach was functioning normal. No change in air suspension or braking. Was close to home so back on the road. When I was parking the alarm went off for a second and i noticed when this happened the gauge momentarily went to normal and then back to zero. I did not have time to troubleshoot but I did disconnect the connection to the gauge and reconnect a couple times with no success. Tomorrow I was thinking to switch the leads on the front and rear air gauges and see if I can make the front gauge work with the rear plug and see if the rear gauge will work with the front plug. What say you guys?

More than likely you have a bad sending unit. If they're Stewart Warner the best place to get them is Summit Racing. I put a T on mine with manual gauges after the same thing happened to me that way I could double check. I also carried a spare sending unit.

[noserider]

Originally Posted by DD788Snipe

More than likely you have a bad sending unit. If they're Stewart Warner the best place to get them is Summit Racing. I put a T on mine with manual gauges after the same thing happened to me that way I could double check. I also carried a spare sending unit.

Yes they are Stewart Warner. I just read some stuff on VDC issues. Sending unit would be much better problem. Where were yours located and any way to test? Thanks

[JFXG]

VDC problem. Well documented issue on some Freightliner MH chassis of this era. I had the same problem a few years ago on my ‘02 DS. I knew it was an indication problem because the actual pressure simply won’t fluctuate like that.
VDC is located in the engine compartment, along the right hand sidewall. Gray plastic body, about the size of a standard paperback book, with electric AND air lines connected. It’s a PITA to get at from either the back or the bedroom hatch. Had Gaffney replace the VDC when I was in for service. Solved.

[noserider]

Originally Posted by JFXG

VDC problem. Well documented issue on some Freightliner MH chassis of this era. I had the same problem a few years ago on my ‘02 DS. I knew it was an indication problem because the actual pressure simply won’t fluctuate like that.
VDC is located in the engine compartment, along the right hand sidewall. Gray plastic body, about the size of a standard paperback book, with electric AND air lines connected. It’s a PITA to get at from either the back or the bedroom hatch. Had Gaffney replace the VDC when I was in for service. Solved.

Ok. It sounds like a common problem and I did some more reading on the cold solder joint repair of the VDC. I would like to rule out the gauge and sending unit before I replace the VDU or repair the joints. Any troubleshooting advise for the gauge and sending unit. I'm thinking just switching the connectors on the working front air gauge to rear should eliminate the gauge.

I also called Freightliner when I pulled off the road yesterday to discuss the issue. The Tech mentioned nothing about the VDC and said to look into Service Solution 3714 which had to do with changing old style connector of some sort. A search on the web did not turn anything up on 3714.

[noserider]

Went to the coach today for some troubleshooting. Started it up and no alarm and both gauges working. I located the VDC and reset both electrical plugs just for good measure. I went for a drive and about a mile down the road the alarm came back on and gauge to zero again. I drove to a parking lot and with the engine running tapped on the VDC. Back inside the coach and all normal. I starting to leave and as soon as I released the parking break the alarm came back. Again back to the VDC and tapped on it. Back inside and all normal again. I shut the engine off and swapped the connectors on the front and rear gauges. Again off for a ride and could not get the system to fail. I think I'll drive it like this for a while and see if I can get the front air gauge to fail this time since it's now getting it signal from the rear which was the one failed. I'm pretty sure tapping on the VDC two separate times and getting that result was not a coincidence. When I get the problem to reoccur again I will pull the VDC and repair the solder joints. I also located the buzzer in case I need to temporarily disable it for my sanity.

[noserider]

What do you guys think? 100% VDC?

[garry1p]

When it comes to fixing problems I never say 100%.

Even looking at a flat tire I still hold off on 100% after all it's only flat on the bottom.

[noserider]

Originally Posted by garry1p

When it comes to fixing problems I never say 100%.

Even looking at a flat tire I still hold off on 100% after all it's only flat on the bottom.

Yeah I agree. OK how about 90%?

[SteveR161]

Originally Posted by noserider

Yeah I agree. OK how about 90%?

Our rear air gauge has been performing like yours for the last 2 years. I unplugged the buzzer. The red low air dash light still activates. These are self healing intermittent occurrences. Pretty sure its the VDU but have not repaired or replaced. Most tutorials say to have a new VDU on hand just in case of failed resoldering efforts. If I really lost the air in the rear tank, the coach would let me know.
Some day I will attempt the repair as well.

[noserider]

Originally Posted by SteveR161

Our rear air gauge has been performing like yours for the last 2 years. I unplugged the buzzer. The red low air dash light still activates. These are self healing intermittent occurrences. Pretty sure its the VDU but have not repaired or replaced. Most tutorials say to have a new VDU on hand just in case of failed resoldering efforts. If I really lost the air in the rear tank, the coach would let me know.
Some day I will attempt the repair as well.

Thanks for the comment Steve.

[noserider]

I got the low air light/buzzer and rear air gauge dropped to zero today. This time however I got the fault on the rear air gauge and had the front air gauge connector attached. I switched them waiting for the fault to reoccur. If it was the VDU the front air gauge should have quit. Hmmm. I really thought it was the VDU but it looks like the rear gauge is the problem.

[noserider]

Anyone have their Borg Warner air gauges rebuilt? Prices for a new gauge seem to run $260-315.00 for the same gauge .

[Skip426]

Originally Posted by noserider

I got the low air light/buzzer and rear air gauge dropped to zero today. This time however I got the fault on the rear air gauge and had the front air gauge connector attached. I switched them waiting for the fault to reoccur. If it was the VDU the front air gauge should have quit. Hmmm. I really thought it was the VDU but it looks like the rear gauge is the problem.

The gauges respond to a specific signal from the VDU , no mater which connection they're hooked to.

Have you had this document?