Weird overcharging issue

if it is the '70 up system (no wire would resistors on bottom of reg) then (1) check that the reg is grounded to the firewall (pull it & scuff both reg/firewall) and (2) check the brushes in the alt for looseness/anything improperly touching that you can see (30 what Del said, the green field wire needs no loose connections/terminals on either end of it (as he said might be going open/closed). It ain't the reg (if it is electronic (no resistors) cuz when they go bad (open or FF) they stay that way. if its a wire wound "box" reg definitely replace it ASAP. As you know FF will fry stuff fast/does alot of system damage. also might be a part time open in the alt. EDIT clean bulkhead also