Anybody know what this is for ?

[hayhauler71]

I am going through my original wiring harness on my 71 chevy c10 350 3 speed manual trans has no ac, ps, pb I ran across this wire that is dark brown in color that comes out of the bulkhead and was in the firewall gutter and not used. It is key on fed and the wire is only 12 inches long and will not reach the engine at all. I have looked at the wiring diagram and in the bulkhead there is only 1 brown wire that is for the voltage regulator and this is about 5 feet short. Any ideas I really would just like to know what it is used for. Here is a pic of the wire and the plastic connector. Thank You