The problem with working on a 12 volt conversion is that you're not sure what has been done. The original system had a 6 volt generator with an external regulator. The common way to do a conversion is to use an internally regulated alt, and remove the 6 volt generator and regulator setup.
Ive seen trucks where an internally regulated alt has been added, and wired to the old 6 volt regulator. Of course it usually doesn't work right. Ive also seen externally regulated alternators wired to the 6 volt regulator, and that really doesn't work.
A 12 volt generator and 12 volt regulator can be used, and that will work provided its done right. You could also wire in an external regulated alt with the matching regulator, and that would work too.
First, you've got to figure out what has been done to the truck. If you've got an externally regulated alt, it must use a regulator for an alternator. I don't think a regulator for a 12 volt generator will work properly with a 12 volt external regulated alt.
If you have the external regulated alt and the right regulator, then you've got two choices. Either wire the existing charging system into the new harness, or remove the alt and regulator and install an internally regulated alternator.
To wire an external regulator correctly, you'll have to find what car the regulator was originally for. Then find a wiring diagram for that car and wire accordingly. Not all 12 volt regulators were wired the same.
Of course, the easy way is to use an internally regulated alternator and the new harness with no mods. Its easy assuming the alt brackets will fit an internally regulated unit.
