Why does a serpetine belt keep coming off. on 1998 Chevrolet Monte Carlo

The origanial belt was replaced a few years ago, then all of a sudden the belt came off. Replaced it with a new belt and it will not stay on. Could it be the auto tensioner is worn out?

Asked by for the 1998 Chevrolet Monte Carlo
1 answer
My suspicion is the auto belt tensioner is worn causing the belt to misalign with the other pullies.