Battery/alternator issues...Help!!!!!!!

I have a 2001 Grand Prix with a 3.8L. Yesterday, on the way home from work, the battery light came on and all the lights slowly started to get dim. I did not happen to notice traction lights or abs lights......I don't remember.:banghead: I pulled in to an auto parts house and they checked my system. They said it had a bad alternator and the battery needed to be charged. I barely made it home and the car would not restart. Today , I pulled the alternator off and put the battery on charge. When I got to the parts place, I asked them to check the alternator(off the car). It checked out good. On the way home, I stopped at another place to get a second opinion, and the alternator checked good there too. I went home and got the battery, went back to the part house and had it checked out. They said it had a 100% charge(I chrged it at home) and tested good under load. I came back home and put it all back together, cleaned the **** out of all the terminals and connections, and drove it for @30 miles with every possible light and accessory running, no problems. So I took it back to the first said parts store, and had the car checked on the tester again. All was good, no problems found. What does all this really mean? Anybody heard of 'intermittent alternator problems'? The battery is less than a year old, the alternator is original. The terminals we really not very dirty. I just don't understand what is going on with this car. Any takers?

You may want to check the chassis ground......it is around the bottom of the battery tray......not sure it is in the same spot on yours

Lead corrosion isn't like rust, it is more like an invisible greasy film that isn't very electrically conductive. The white/green powdery corrosion most people associate with dirty battery cables is a reaction between battery acid and the copper of the cable. In short, the cables don't have to look dirty to be dirty.

Thanks everyone. We'll see what happens.

I had a GM alternator from a "W" body car tested at Autozone and it passed their test which evidently doesn't represent realworld load conditions. I wound up replacing the alternator to correct the abnormal charge indicator light. The device that monitors the output of the alternator and charging system is the PCM. If it senses a voltage below or above the programmed threshhold it will trigger the light. I'd keep an eye on the alternator and keep it at the top of the suspected parts list. Easy circuit to troubleshoot with a multimeter if you get the problem again.

You may want to check the chassis ground......it is around the bottom of the battery tray......not sure it is in the same spot on yours
I did find moderate corrosion on this terminal and cleaned it up......Maybe that is what helped. Thanks for the heads up.