Re: Battery alarm troubleshooting
An alternator consists of a heavy metal frame, which more or less lasts forever, and a batch of cosumable parts. Wire windings, bearings, diodes, sometimes the internal regulator, etc.
Everything in the alternator can be replaced, so the alternator can be rebuilt (which means fixed) or remanufactured (which means stripped down and rebuilt 100% to original specs). Sometimes it is cheaper to simply buy a whole rebuilt/reman'd alternator, with a warranty, than it is to gamble on whether some shop is really qualified and going to charge any less to fix yours, IF it needs fixing.
It really pays to learn how to diagnose them yourself, since there has also always been a thriving community of "see? Your alternator's bad!" thieves around. As well as the nice men who spray the whole thing shiny silver when they've fixed it, which actually guarantees it will burn out again (gee, I don't know why) right after the warranty. All it takes is one extra coat of paint on the new diodes, and they WILL overheat and blow out early. All sorts of little tricks to keep the business repeating.
Best adice I ever heard about alternators, is to look in the shop. If it is a greasy mess? Walk away. Yes, it is a dirty business, and someone who is doing a good job will also usually keep their shop fairly neat.