That's what happened to my "Parts Car" too. I would expect though that if it's the belt the light would remain lit. Still I would take it back to where I bought it (MB or used lot) and give them a chance to make it right. Still, I'm not too sure I'd trust them to fix it right if they said not to worry about it in the first place....gets out the electrical tape and puts a strip over the alternator light "There, fixed good as new!"