Alternator works randomly
I've done quite a bit of research, but I wan't to make sure I don't waste my time. My 2007 ZX3 hatchback Focus recently is having charging problems. The alternator seems to be working on and off at times. While driving and when its not charging sometimes I can rev the engine up to 5k+ and it will kick the alternator back in gear and start charging again for a while. Does that sound like an alternator problem. And why would it work randomly. I'm worried I will take it in to have it tested out and they will say its good when its really not. What should I do?