A4 TDI 130 developed noisy idle

[Mini-mad-matt]

Hi,
My oil level warning light came on this morning, so I popped open the bonnet and gave it a top up.
All seemed well, no oil warning light on, and we went off to Southport to enjoy the great weather. As I came off the motorway and got onto the normal roads, I noticed that the car had starting to make an awful growling kind of noise at idle. If I give it any revs, even upto just 1100 RPM, it stops and sounds totally normal. With the bonnet open, you can see the engine shaking like crazy when just idling and the fan belt almost seems to be jumping about on the alternator pulley. The noise gets worse when turning the steering wheel. What on earth could this be? Any help greatly appreciated,

Cheers

MMM

 

[Mini-mad-matt]

An update:

The noise goes away a bit when I put on my lights, or heated rear windscreen, putting extra load on the alternator.
I also tried to turn the tensioner pulley, and managed it no problem without having to undo anything first. Is this normal?

MMM