Mk5 golf aux belt noise-Tensioner or alt free-wheel pulley?

[nia573]

Im Looking for some advice
Dads 56 reg 1.9 TDI Golf plus has been making some slight rattly noises at idle which seem to come from behind the alternator area & I think it’s the auxiliary belt tensioner. You can see it moving slightly backwards & forwards & Im not sure if this is normal

As soon as I feather the throttle slightly to just above 1k revs the noise disappears

I used my stethescope around this area & its definitely louder at the tensioner area rather than the alternator position

I ‘ve read other posts about similar noises & heard about the alternator free wheel pulley playing up, so I released the tension off the belt & was able to turn the alternator pulley by hand just the one way. The other way it seemed like it wouldn’t turn. (it definitely wasn’t free wheeling / turning easily - which I believe it should?). Space was a bit tight for my fat fingers of one hand (while the other hand held the tensioner off the belt) but it definitely wasn’t free wheeling both ways


Does this confirm that the alternator free wheel pulley is at fault? If so is it a fairly easy fix (loosen tension off belt, lock tensioner in position , remove air hose for access (?), & unbolt to replace??)

Edit - Just looked at this video:
https://www.youtube.com/watch?v=fyosuYbPxr4

& he says the pulley should just turn the one way (which mine does). So is my pulley ok & is it the tensioner that’s causing the issues?
Im confused?!

Thanks for any help