Quote Originally Posted by snakedork View Post
I would say its probably not the alternator. My first check would be for a good ground on the battery. I have had several vehicles that either the battery cables or the ground wire has gone bad. If you have a multimeter check for resistance on the negative wire after removing it from the battery. when you do that check you should have a low reading in ohms. You should also check battery cable to body ground seeing how both the aux. and head lights run off of the body ground not the motor ground.
with your car running disconnect the battery if it dies then one field of your voltage regulator is bad which is usually built in the alternator.