Overcharging 73 Swinger

Mattax said
So the only explanation is that brush and terminal is shorting to ground.
It might be as simple as replacing the brush and insulator or the insulating washer.
I'm pretty sure I have a couple new ones. They look like this (might take a few minutes to load the pics)
Alternator repair, a little show and tell.

This is really easy to accidentally do too, just by putting the insulator on the wrong side of the terminal that the wire goes on.

I have seen and fixed points that people did this with also, and also pretty easy to do.