Sorry for ignoring you for so long. I don't know why I overlooked your reply.
Have you solved the problem? GM did commonly tap off the battery cable at the starter for the other circuits. The starter is not involved in those circuits. It was just a convenient tie point. Those wires are fuse link wires. They are a smaller gauge than the circuit they protect, and the insulation is designed to not burn or melt. They have been known to corrode apart at a splice, but other than that, pull on them to test them. If they're still good they'll act like a wire. If they're burned open, they'll act like a rubber band.
When they do burn open, they leave a carbon track behind that can conduct enough current for a digital voltmeter to pick up and display a voltage. You won't get enough current through to run a test light though. That's why a test light is more accurate in this case, or you need to measure voltages with the switch plugged in and turned on so some current is trying to flow.
Wednesday, January 29th, 2014 AT 7:46 PM