Is there a way to check serpentine belt tensioner?

[Ieatcamaros]

It sounds like your belt is too loose. Your tensioner is probably ok. Try getting a 1/2" or 1" shorter belt. I'd start with one that is 1/2" shorter. The only way to really check a belt tensioner is with the belt off, put your socket and ratchet (try to use a shorter handle ratchet not a long handled one) on it and check it's stiffness. As long as it has reasonable spring stiffness, it is ok. When I reversed my belt tensioner, I had this same problem. I just rotated the spring inside to fix it.