Noise Diagnosis (with video)

[Hurdy]

You'd have to ask. It is the tensioner that squeals.

[TrickGTI]

No one has mentioned that most alternator pulleys are free wheeling nowa days and from the video the aux belt looks to be flapping around alot im going to have a stab in the dark and say its that 
The weather gets into it and they seize up causeing that squeaking noise.

[Steve_PD]

as above sounds just like mine did when the pulley seized.
does the noise get worse when the AC is on or when the steering wheel is turned

[andrewparker]

Is that the aux belt? Because that is exactly where the sound is coming from.

I haven't noticed it get worse when the AC is on but I'll try it tomorrow.

[TrickGTI]

exactly right and even more to the point that is the pulley that will be faulty right bang in the circle you have done 

[andrewparker]

So is the fix to replace the tensioner and belt?

[Saint Steve]

So is the fix to replace the tensioner and belt?

YES!!!!! 

Cambelt and Tensioner must be replaced!!

The cambelt tensioner is right next to your Photo. The aux belt is Not the Cam belt, its behind it
 

Do not replace Aux belt. Its ISNT that. Me and several others have had same issue, all cured with cambelt and Tensioner replaced under Warranty!!

[TrickGTI]

Im not saying dont get the cambelt done as thats what the noise proberly is. But the alternator pulleys arnt a un common thing to go wrong so dont be suprised if you get the cambelt and that done and it might still be makeing the noise. 
lets us know what it turns out to be.

[andrewparker]

The VW Technician did think at first that it might be the alternator belt (as did a few other people who looked at the car), but I got the car back today with a new cam belt, tensioner and water pump, and it is squeak free.

[Saint Steve]

Woohooooooo!!!!!!