The alternator will not cause the overcharging condition. It only does what the regulator tells it to do. The regulator is built into the engine computer, and even though computers are extremely unreliable, it's not common for the regulator circuit to fail.
Thetoolman is right about measuring battery voltage when the problem acts up. You can watch the brightness of the dome lights too. Before you hop out of the truck, shift into reverse and watch if the voltage gauge drops to normal. If it does, suspect a grounded wire between the alternator and the engine computer. That wire goes from the alternator through the Power Distribution Center on the left fender to the computer on the right fender. When shifting into reverse, the engine rocks on the rubber mounts and will move wiring harnesses causing problems to come and go.
Tuesday, April 14th, 2009 AT 3:38 AM