New tension pulley and belt fitted with squeaking

[deen0]

I recently fitted a new tension pulley and a new belt. Its all fitted correctly and is an auto tension pulley but its squeaking at around 1000rpm - 1500rpm anything above and below it doesnt do it. Any ideas on what this could be? The sound is almost definatly coming from the tensioner. I have tried loosening belt and tightening it more but nothing will get rid of squeak any help wiuld be great thanks.

 

[Sean6545]

Either the belt hasn't been aligned on the pulleys correctly or the tensioner has been fitted wrong.