Wiring Question -- Which Wire?

Dustin, one of the old(er) timers like JRichker will be able to say better, but I believe that Ford has used that wire color for the alternator switch wire forever. This might be part of the circuit you're seeing (though I need to check schematics because I thought the alt wire was of small gauge - smaller than anything going to the Ignition itself. There might be a tee with a smaller tributary splitting off however).

On the alternator aspect: Fox and SN mustangs have a 500 Ohm resistor built into this wire (in parallel) in case the battery light burns out (the regulator is on the far end of the wire, and supplies ground when the alt is not excited, and removes ground when the alt excites). On your older car, this could be a similar situation.

Just an idea for your or someone else to agree with or refute.

Good luck.

Actually, that alternator wire is both colors. I have the sinking suspicion it and the TFI wire you're looking at are one in the same at the ignition switch.

You probably have been looking at them already but just in case:

alternator wiring and ignition switch wiring

Good luck and bump for ya Dustin.