DJMarty,
I'll try to look it up in my Bentley Tonight. Is it showing up in VCDS as a "demister flap blocked" trouble code?
I had a similar problem with a "stuck" main flap in my '99 audi A4. It turned out to be the climate controller itself. The climate controller, send a + or - voltage to the flap to move it, and the flap has a potentiometer for the controller to check the flap's position. My climate controller was failing to send the voltage to the flap, then threw a "flap blocked" trouble code when the flap didn't move.
A used climate controller off of Ebay fixed my problem, after I found no flap probelms.
I'll let you know what I find in Bentley...
Daniel