The OP's profile says 1984 F250, and he states he has a 6.9.

1983/85 F250/350: There are 7 different alternator wiring harnesses, SEVEN!

It makes a difference if the truck has a 40 - 60 amp alternator with gauges or with idiot lights.

Ditto for the 70 amp alternator.

If I knew exactly what the OP has, I might be able to locate a new original harness, that's been obsolete since grandma was a girl.