The signs of a bad drive belt tensioner include.
Squealing noise.
Loose drive belt.
Uneven belt tracking.
If the drive belt is off center, is at the edge of the pulley or has flipped off the belt tensioner then it may be bad or misaligned.
Another sign of a bad drive belt tensioner is if it sticks or has notchy movement or is hard to move.
If you move the tensioner with a wrench or your hand it should move smoothly.
If the drive belt tensioner sticks or is hard to move or notchy feeling then the tensioner bearing surfaces are likely worn.
If the drive belt tensioner's arm and the spring case is making metal to metal contact then the bushings are likely worn down.
A squealing noise that comes from the drive belt even at low engine RPMS or the drive belt comes off the pulley or partially off the pulley can indicate you have a bad drive belt tensioner that needs replaced.
The drive belt also known as the serpentine belt is what's essential to many vital vehicle functions.
If you hear a squeaking or grinding sound, especially when starting your vehicle, it may be time for a drive belt tensioner replacement.
The average cost for the replacement of a drive belt tensioner is between $125.00 and $380.00 but can vary from shop to shop.
If you can replace the drive belt tensioner yourself it can be cheaper.