Auto dimming rear view mirror not dimming any more??

[S3 Paul]

Recently i noticed the rear view mirror seems to have stopped working,
It did work a while back and nothing has been removed / replaced that should effect it.
Has anybody any ideas where to start??

 

[Greg-S3]

Mine has done that to mate, it's the gubbins inside that give up, mine looks like its half yellow and half normal! I think the only way round it is to replace the mirror! Not expensive on eBay if you find one!