had the same problem. its the blower unit. Located in the back of the glove box. Get a haynes manual to tell you how to take the complicated trim off.
The blower is located behind the air bag. It tells you in the manual to take the air bag out, (no need if your careful) Very easy job,took about twenty mins.
Also a vw brand blower costs £350. I can a non manurfacture one for £80
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.