[Daves55Sedan]

Okay so, everything installed, I go out to start the engine for the first time. A few seconds later, smoke starts coming out of the dashboard and a smell of burning plastic. I shut the engine off and disconnect the battery again.
After blowing the smoke out of there, I stick my head up under the dash to inspect the damage. The entire black/green circuit from the "ACC" terminal of the ignition switch to the gauges has all the insulation burned off. It got so hot that it burned through the electrical tape holding the wiring harness together.
First I closely inspect the whole thing and confirm again that the wiring was NOT touching ground or smashed between the instrument cluster clamps or anything like that. Right now, I am stumped as to why this happened. This was a brand new repro wiring harness circa 1995ish.
So far I have removed the burned up black/green wiring and have made a new guage power wiring harness ready to install. Before I bother with that, I am going to disconnect both sensor wires and test for continuity between each guage terminal and case ground. To my knowledge, if everything is right, the readings should show maximum resistance, right? And if it doesn't, that means that the internal wire inside the guage is touching the guage housing. Gonna do that first thing in the morning.
If that is okay. Then I am going to first re-connect both sensor wires and attach test leads with alligator clips from the BATT terminal of ignition switch and reconnect the car battery cable. If the gauges operate without catching on fire, I should then be able to disconnect the test leads and install my home-made guage wire harness.