Try this; remove the belt, position the tensioner roller where you can easily get your hands on it to move it both directions and then tighten the center bolt. Now try moving the tensioner roller/outer housing in either direction. If it moves and doesn't return to it's original place, then the rubber is sheared or otherwise destroyed. Replace the tensioner. If you can move it just a little bit, and it returns to the original starting point, then it may be ok and you need to look further into it. Check to see that when you turn the adj. rod nut, (with the center bolt slackened and the belt still off) that it actually rotates the inner part of the tensioner. Normally, the outer part should move with it.

If you need to replace the tensioner, they can be found for under $90. I just replaced mine about 2 weeks ago, and the quality appears to be the same as the original. PM me if you'd like the link for the supplier.

Gary