[72gmcshorty]

On my wiring harness, at the firewall junction, on the top row. One Red , one black, one black with white stripe. I know what the red and the black with white stripe are for but what about black? It's not in my wiring diagram. Its a 72 harness.

AND after doing the removal of external regulator, I should get a complete circuit from the tan wire in the harness to the white wire going to the alternator, correct? (when using a tester)