Remove the serpentine belt and check the belt and pulleys for damage. While the belt is off, turn the alternator by hand listening for the noise.
Possible problem with the alternator. Could be source of the noise if it's bearing is going out.
If you're describing the idler pulley or the tensioner pulley, it's probably a bad bearing. Pulley bearing failure is common and relatively easy to repair. Remove tension from the serpentine belt then turn the pulley back and forth with your fingers. It should make no noticable noise and should turn smoothly. If you can hear any grinding noise or if the pulley feels like the bearing is grinding, replace it.
It could be a loose serpentine belt. Or if the alternator is going out either way its most likely a charging problem.
Probably the serpentine belt idler pulley bearing.
To diagnose a noisy pulley, remove the serpentine belt and turn all pulley's by hand. Try to notice which of the pulleys make a grinding sound or feels loose. Even an alternator bearing can sound like just another bad pulley bearing, so don't assume that the alternator is okay. A bad bearing often feels like there are little grains of sand inside when you turn it manually, but sometimes it's difficult to detect the problem if you haven't had the experience. Note, before you remove the serpentine belt, make certain that you have some kind of drawing or a good mental image of the routing so that you can put it back.
Might be that the nut holding the wheel bearing needs tightening or that the wheel bearing needs replacing. Going to have to take it apart to get to the bottom of this one.
Your battery is not being charged because of a problem with the charging system Whether its a problem with the alternator / voltage regulator , the serpentine belt etc . you should have the charging system checked
There is no problem...the problem was the alternator. You have fixed the problem.
It could be that the belt and alternator are not aligned properly resulting in uneven pressure on the wheel of the alternator damaging the shaft or bearing. Also, excessive torque on the belt might cause the same problem.
Usually no warning signs unless a bearing is going bad, Other than that it just stops charging the battery. what about overcharging? alternator is 10 months old, as is battery, same problem
I am having the same problem with a 99 Protege. I have changed the alternator and aligned/cleaned the pulleys and the problem persists.I replaced the alternator, on my 1997 Mazda Protege, seven times before someone figured out why the serpentine belt kept breaking. It was the belt tensioner! It had to be removed and rebuilt. Now it is working like a charm!! And I havn't had to replace the alternator in over 3 months!!!!
There could be so many problems. Batery, starter, alternator, serpentine belt, no spark... the list is endless. spark plugs? spark plugs?