after 25 years of adding/removing stuff to the one I bought new in '86, I don't have a clue what all the wiring is...and I have taken the side cutters to it at least three times trying to clean it up.
The one I bought back in '99 for my son had messed up wiring and I took my side cutters out and removed four different alarm systems that had been installed on it by po's, discovered an external pump in front of the fuel tank that was wired directly to the fuse block with no relay plus a whole bunch of other things. Then there was the El Camino that I bought that had been wired with lamp wire...yes, the kinda wire that you plug the lamp into the wall with. Someone had installed power locks, alarm, etc and lamp wire was his choice of wiring. I cut about 30 lbs of wiring out of that car before I found why it did not want to turn over.
Side cutters are my best friend
It is frustrating trying to help someone that does not know an amp from an ohm....I think E=IR went out of existence along with crystal set radios