There are two screws on the back of your alternator. They hold your voltage regulator in place. Remove the unit and check the brushes. One of them is probably severly worn, and only making occasional contact. This will cause your lights to glow dim. In Virginia, you can replace the whole unit for around $60.00. Also pull the lower splash pan and check the wires that run from the alternator over to the drivers side of the car. They overheat over a period of time and the insulation becomes brittle and falls off. Since they run against the engine, they short out against each other or the engine. Good luck.