Yesterday my battery warning light came on, on the way home from work. The volt guage was reading in the normal range, but it was on the low end. Whenever the rpm got over 2500 the light would go out. As soon as they dropped back below 2500 rpm it would come back on. The headlights seemed a little dim as well. On the way to work this morning, the battery light was still on, and after a couple of miles the voltage gauge went to zero. I returned home and took the other car to work instead. About an hour later my wife calls and tells me the truck won't start. [ 7.3 powerstroke] Any of you guys in the wonderful world of GT know which one it might be? Which one should I check first?