Dave, I'm hesitant to post(but when has that ever stopped me) because the thoughts in my head are you fixed an intermittent poor connection, but it wasn't the ground circuit for the cluster which helped your charging and lamp test function. That's because the ground for those things is not inside the car at all. It is that blue wire between the alternator frame and the bracket bolt on the block.

If you follow that circuit Phil says needs two sides, the way it gets back to the negative terminal of the battery is through the alt. It is the positive side it needs from the instrument cluster, when the key is on and the motor is not running. Same for providing the pre-exitation (D+) voltage to the alternator.

The result is great and not to take anything away from that, but if now you know exactly where the ground wire for the cluster makes its contact with the transmission hump sheet metal, you could lift it off and test with it completely missing. No doubt there will be some interesting results, which might be valuable to those who troubleshoot by symptom/cause tables, but I'd like to know if your lamp test function then stopped again, and your charging voltage disappeared.
--
Art Benstein near Baltimore

I used to be indecisive. Now I’m not sure.