I agree with above. You need to study OEM wiring diagrams. There is no actual grounding wire in either of the 2 harness connectors to the inst' panel. Early on in production, they did place a small ground jumper on the screw that holds noise capasitor to housing. It ended at radio support screw to dash if my memory serves. We've seen very few photo examples of this lil jumper. Their engineers and bean counters decided that was unnecessary time and coins. The pot metal inst' housing should find a ground through the few screws that hold it in the dash.
I'm wondering if there is a bunch of painting or powder coating in play here. That will interfere with ground path.
