The VDC sends data to the Message Center (the 24 light bar). From there, the Message Center drives all of the guages. If the Message Center has no power, then all of the guages will not work.
When Freightliner sent you the "trouble shooting guide for the Type XC chassis with Type III wiring", was it Service Bulletin 54-12? SB 54-12 has extensive troubleshooting steps, but some are complex. If you don't have it, here is a link to download SB 54-12.
Freightliner SB 54-12I think you may have a simple loose connection, blown fuse, or bad relay somewhere.
When you called Freightliner, was it the Freightliner Help Desk (1 800 FTL HELP)? They are usually very good with diagnosing problems. If your call was not to the help desk, give them a call with your VIN number (last 6 digits). It's free.
At the very least, I would verify all fuses that could affect the VDC and Message Center are good, and all relays in that circuit are also good. Freightliner has a lot of relays in two boxes that are located by the builder when they build the coach. Mine is in the first bay driver side. All of those relays (at least on my coach) have the same part number. Don't be afraid to swap those relays with same part numbers to see if the problem moves.
I would also disconnect all connections to the VDC, check for corrosion, bent pins, or other obviously problems, and then reconnect. Also check for a connector on or near the Message Center. Sometimes an unlocked connector can work for years and then finally vibrate enough to cause a problem.
If you get any more symptoms or clues, post here and we'll try to help. You might also post in the Freightliner forum over on IRV2. This would give you some more exposure to Freightliner chassis owners.
When you or Freightliner solves the problem, please give us an update.
Fred