John, as Mel suggested, you may have a bad ground. There are ground buss bars scattered over most Monaco coaches. Find each one, spray them with WD-40, loosen each terminal screw and re-tighten. Sounds too simple, but it has cured dozens, if not hundreds, of electrical "gremlins". If that does not work, tilt the dash outward and do the same with the daisy-chained grounds on the instruments.
Van W 2000 Dynasty 36, pulling one Harley