I'm having a problem with the 6v generator in my Type 3 Karmann Ghia; the generators keep dying and I don't know if it's a problem with the "car" or a problem with the generators. I've had 2 generators self-destruct. When I first install them, I got a lot of sparking from the brushes, and eventually one or more elements on the commutator let fly. I have never, ever seen this happen to a generator before. When the generator was sparking, I was still getting voltage, but once the commutator destructed, I didn't, because it kicked the brushes out.
Any idea what would cause this?