Hello all I just installed a new belt tensioner on my truck. This one is wobbling right now. The old one did not do this. The reason I changed it is because the old one was making my belt squeek and was separating in the back. Any ideas as to why it wobbles? I added a video to you tube and will post the link here. Also when shutting the truck off there is a small squeek.....that's the only time it squeek now

 

Sounds like you have a faulty tensioner. I would take it back to the parts store and turn it in for another new one.