To see how your instruments work, click the link below. It is a Freightliner service bulletin that describes your coach's instrument system.
Some VDC's have been known to have cold solder joints. Look in the files section of this IRV2 forum and you'll find a document describing how to repair these cold solder joints. Repairing the cold solder joints is an inexpensive fix compared to buying a new VDC. I am still running the original VDC in my 2000 year Freightliner chassis with no problems, so some but not all of them fail.
You'll also find some other posts about the VDC's in the Freightliner section of this forum.
Keep us posted when you find the actual problem