Idler pulley?

i have a similar problem with my idle and also i think i need a new alternator. that sucks. after driving my car hard the other day i came home to hear this weird whining noise, sounded like a belt or a pullley, and when i popped the hood, the noise was coming from the alternator. its not the alternator, but the pulley, i think the bearings are shot. anyone know of this problem?? im hoping i can just change the pulley, instead of getting a new alt., but im not sure

ohsoslow- The idler pulley is used to adjust the tension of the a/c belt. The idler pulley is most likely snot the suspect of your vibrations. I think you should feel a little vibration just b/c of the age. Unless your vibration is abnormally harsh than I would worry about it.

Silko82ny- I bet the noise is coming from the idler pulley and not you alternator. I had the same problem where my bearing actually seized. The noise seems to coming from the alt b/c of the proximaty of the idler puller. Just replace the pulley($60) and the noise should be gone.