[chevy_mike]

I ran into this problem on my '65 C10. We found a wire that connected to the ignition switch, that looked okay, had broken internally and when we brushed up against it, the insulation finally let go and we could see the broken wire. We reconnected that and all the charging issues went away for the 3+ years I owned it.

Try gentally pulling on the wires connecting to the ignition switch and see if any come loose.