Air problem, location of VDC?

[smlranger]

My front air gauge acted strange on our recent trip but we had no problems. This AM while taking the coach for some minor body work, the front air gauge dropped to zero and the low air alarm and light came on. I stopped and checked for any audible air leaks and, finding none, continued. The air qauge would jump to normal readings then go back to zero. This continued intermittently for the entire one hour trip. I had no problem with brakes or any symptoms of air loss.

I called Freightliner and they immediately said the VDC was bad and would need to be replaced. He said it was a 8" square gizmo with one green and one red air line connected. He said every coach manufacturer mounted them differently but advised Winnebago usually put them in a rear compartment hidden behind a panel.

Wondering if anyone has had occasion to locate this device on a Journey/Horizon of my vintage?

[smlranger]

My front air gauge acted strange on our recent trip but we had no problems. This AM while taking the coach for some minor body work, the front air gauge dropped to zero and the low air alarm and light came on. I stopped and checked for any audible air leaks and, finding none, continued. The air qauge would jump to normal readings then go back to zero. This continued intermittently for the entire one hour trip. I had no problem with brakes or any symptoms of air loss.

I called Freightliner and they immediately said the VDC was bad and would need to be replaced. He said it was a 8" square gizmo with one green and one red air line connected. He said every coach manufacturer mounted them differently but advised Winnebago usually put them in a rear compartment hidden behind a panel.

Wondering if anyone has had occasion to locate this device on a Journey/Horizon of my vintage?

[chasfm11]

There are really several "boxes" that have to mounted and all 3 of them on mine are in the same panel - in the last compartment on the passenger side. The TCM (transmission controller), the VIM and the VDC are located together. My guess is that the wires are all the same length on the Freightliner chassis so it has to be somewhere on either side of the engine. From underneath, you should see a major wiring harness coming from the front to back. Following that on mine leads you directly to the back of the compartment where the 3 boxes are located. The red and green air hoses are not visible until you are inside that compartment on mine so I doubt that tracing them would help you.

I hope this helps.

CHarlie

[KIX]

Not sure how much help this info will be but on our Spartan chassis the VDC issmounted on a cross frame member just aft of the generator. AS you were advised there is a red and a green air line and either one or two multi wire connectors. Very easy to change out......when you locate it.

[AA4WP]

This subject is so fascinating to me. What in the world (or on a diesel chassis) is a VDC? While on that subject, can some one tell me (us) where there is a reasonably comprehensive source of diagrams, theories of operation, etc. I tried the web site at Freightliner and they seem to have a manual for $95 which may or may not tell of such things. I am lost after transmission, engine, differential, and perhaps air brakes. Everything else is a complete mystery to me.

Thanks in advance (and I didn't mean to hijack the topic)

Wendell

[autofish]

Had the same problem on my 01 Horizon. The vehicale date computer is located on a fire wall under the bedroom engine access cover hard to get to. The resson mine failed was from heat as it is mounted too close to the turbo and the radiant heat killed it. Could not relocate new one so made a heat sheild from Al. plate. That was about 4yrs and 39k miles ago so so far ok. Just don't let the dealer replace it with out shielding or it will fail again. good luck hope this helped.

[chasfm11]

Wendall, there is no real manual for how the chassis works. I suspect that this because each manufacturer believes that they have trade secrets that they don't want to share with others.

Here are a couple of suggestions to help you further your education.
1. Google "Controller Area Network". This is the computer protocol used on modern MHs and many large industrial machines. I'll warn you in advance that this is "computer geek" stuff but if you read through the articles, you'll learn about the standards and how things data is passed.
2. Call FCC and request the detailed wiring diagram for your chassis. While it is a very complex "spagetti" chart, it will show you how the various chassis components that you are are connected together. You are lucky - Freightliner will give it to you. Some other makers will not.

I had a highly intermittent speedometer problem on our MH that Freightliner had tried to fix several times but couldn't. After studying the information that I outlined for you, I fixed it. It turned out to be a bad connection on the VIM.

I suspect that you would be surprised about how the engine and the transmission (ECM, TCM) are integrated into your chassis. It may be a lot different that you currently believe.

[skigramp]

SML ...

On my 2004 Journey there is a black square gizmo with a red and green hose behind the panel (same one as where the trailer fuses are located) in the power bay on the driver's side.

Here

[ROY120]

Hi smlranger
The vdc unit you desribe can be found under the second engine cover underneath the bed it is the second box in on the back wall you will see the pipes going into it.

Roy
Journey 03 DL

[RLS]

Gary, Do a search for VDC repair. The unit may have bad solder joints. I ran across the repair some time ago but don't remember where I saw it. From what I remember Freightliner had a bad batch of VDC units during the 99-01 chassis years. They were built using a process called wave soldering. This is great method to assemble regular printed circuit boards. The VDC units have some components that are to big for this type of soldering. If you find the write up, it will describe how to fix this yourself. Have a happy thanksgiving.

[indiana journey]

smlranger, Sorry to hear about your problem with your VDC in your coach. We had a problem with the VDC in our 2004 Journey. When Freightliner replaced the unit they told us that the air lines going to the VDC needed pigtails or a loop in the them to help keep the moisture out of the VDC. It has not given us any problems since putting the loops in the airlines and replacing the VDC. Hope this helps you solve your problem. Good Luck, Indiana Journey

[smlranger]

Thanks for all the helpful replies. Another forum member told me he was having a similar problem with his front air gauge and discovered a loose wire on the gauge. I plan to check for that before I attack the VDC.

[Navy Flier]

I agree with autofish and roy120 as to location. On my 03 Horizon 36 the VDC was located under the front access cover under the bed. It was attached to the back side of a cross member and easy to see and access. If it is not there contact Freightliner. They installed it and should know where it is.
For those who were wondering what the VDC is, it is the Vehicle Data Computer. You can think of it as the brain for all of the dash gauges.

[autofish]

When I replaced mine I talked with frieghtliner and they told me they do not place the vdc but leave it hanging and it is up to the MH BUILDER TO PLACE so think it is a Winabago problem.