I have a 1991 chevy 1500 4X4 350. i was driving it and the battery light came on so i checked the voltage and the alternator was not putting out. so later i got back in my truck and started it up and the alternator was charging again. when im driving every once in a while the headlights will get real bright and the battery light will come on as if its charging real high, this happens for a few seconds and returns too normal..... could it be my alternator? does the alternator have an internal voltage regulator???