Fan belt tensioner movement

[beexy]

Have just had my fan belt tensioner replaced as well as the belt. Has been running fine until today when. I put the air con on. Started getting that horrible fan belt noise again but only when idling. Had a look under when stopped and noticed the tensioner appears to be moving up and down a bit with a bit of a "clacking" noise. Anything to be worried about?

[GQtdauto]

From memory it does move a bit as load is placed on the alternator etc .

[beexy]

I have since had a proper look beneath and have seen that the pivot arm is just swinging around loosely. Looks like the screw holding it on has given way. Now causing the belt to be loose when not under load. Any idea what may have caused this?

[GQtdauto]

If you've just had it replaced sounds like mechanic has either not replaced it or broken it somehow .