[john walker's workshop]

the problem with just replacing the regulator is that the regulator's brushes usually have worn deep grooves in the alternator's thin commutator, sometimes most of the way through it. so the life of the commutator is very short and the brushes often don't seat well and/or get chewed by the rough commutator grooves. the commutator is too thin to machine smooth again, so it needs to be replaced. quicker to replace the entire unit.