Well after rebuilding the headlight motors and sourcing out the electrical problems that I never had before putting these headlight motors in (these came out of the gt I bought in December, my good ones from this notchy went into the gt), all worked fine and looked and sounded good, that was 2/2/14. Had to go out to the garage tonight to get a wrench and it is full of smoke and I can smell something burnt, thought battery overcooked at first so I checked that and the bikes, then noticed the turn knob on the ds headlight melted off and motor to hot to touch. Guess I will be looking for "new" ds motor and tracing wires again.
I had loaned one of my Fieros out while a friend's was being worked on. The passenger headlight failed during that time and only went halfway and stopped. He left it and it did the same thing. Totally melted. The only thing inside worth saving was the small metal gear and the shaft and drive plate that goes through the larger gear. The burned smell from taking it apart in the garage lingered for over a month.
Apparently it was internal and the limiter switch didn't break. I replaced the complete motor and nothing else without any future problems. I've also found this to happen when a motor is freshly rebuilt and the rubber weather seal at the top slips out and lodges underneath the knob during reassembly. If you have another limiter switch assembly, by all means use it in your replacement motor. Don't use the one from the burned motor.