[5potnoodle]

I'm presuming you mean that your blower stops running, or do you mean the display goes blank?

Had a problem in both my 89 200 quattros, it was the blower motor brushes failing to make contact with the armature. If I went round a bend (can't remember which direction now), there was enough play in the blower motor bearings to allow the part of the armature which hadn't been subjected to 250,000+ miles of brush wear to allow contact, but going straight and it would stop again. If I was parked and started the engine, I had to lift the hood and bash the top of the blower housing to get it to run so it would demist the window before I could drive off. After not being able to source a replacement (didn't know about the C4 system swap option), it eventually packed up completely. I didn't have anywhere to store her to fix later so I had to sell the car to another enthusiast for restoration. It broke my heart.