fan belt rubbing when lights are on!!

hi
this is a problem i've had for a while and has been in and the gerage for some time.
when i run the car during the day it runs great but when i put lights or radio on i hear a squeling noice from under the bonnet. i did bit of of research and found with the bonnet open and enginge running i turned lights on to see the fan belt move slightly which caused it to rub on cambelt cover. why would it do this.
Number on alternator is 026 903015 0r 0120489362 363 and k1 14v 23/55v its a 18gti cabrio here are some pics
any help advise would be great

The fan belt is slipping so it needs tightening up or it will glaze and not work at all and the car won't start! it's slips with the lights on because the alternator is under load from the lights drawing juice from the battery  :mrgreen:

the fan belt was only fitted by a garage 4 weeks ago. should it need tightening up also this is the 2nd fan belt in about 8 weeks the last one snapped!!

make sure there is no bearing play on the alternator, I had the same problem by a garage and it turned out they had fitted the wrong one, so a proper one and a tighten up happy days.

thanks guys, if you look where arrow is your see where the previous owner has put some rubber!!
chortle when you said garage put wrong one on do you fan belt or altanator. also why would fan belt move move?

The 'rubber' is a plastic bung factory fit that covers the access hole to VWs comedy idea of a blind Allen key to adjust the alternator.

The bottom crank pully looks brand new? Are all 3 pullys in line?

Also the early belts do stretch and slip a bit esp initially, later ones moved to the Ploy-Vee types. I'd try and tighten it up a bit more.

thanks early-1800 feel a bit stupid now lol i will have a chat with garage in the morning yet again

the belt they put on mine was too wide so the V shape did not sit in the groove of the pulleys properly.

so just to make sure it will move left to right on pully if i turn lights on if belt is loose

yea itll just move generally more

ok thanks everyone will let you know outcome

just to update everyone the bearing's had gone or going in alterntor. thanks again for the advice

you will need to retighten the belts after while when fitting a new belt, they do stretch a bit as they bed in. 5mm deflection is what you should set it to