1987 300E - I tried replacing my belt tensioner damper earlier today, but I ran into a problem getting the belt off. I loosened the 19mm bolt several turns, and I unscrewed the tensioning nut until it was completely slack, but I couldn't get the pointer to move more than about 1mm right. It moved slightly, and then stopped, no matter how much I turned the adjustment screw. There was no noticeable change in the belt tension, nor when I tried retightening the adjustment screw. I suspect my belt tensioner is shot, but can anyone explain what might be going on?

thanks,
anthony