Sounds like your on the right track with a poor connection somewhere.
Had a guy with a similar problem with cluster and this is what he found.
"the fault was in the wiring loom in the engine bay between the fuse box and
the firewall (about 18 in) the hood release cable had been
rubbing and shorted the wires. I moved the cable out of the
way repaired the wires and everything is now happy "