[s-cars] No heat

[davidpriebe at cablespeed.com]

I drove my wife's S6 today for the first time in a couple 
of months, and noticed that her heater is not blowing hot 
air. It blows cool air just fine, and directs it to all of 
the appropriate places. But no matter how high I set the 
temperature, no hot air came through. The coolant 
temperature guage is reading the normal operating temp. 
But it did take considerably longer to heat up than does 
my 200, about 5 minutes longer. I have no idea where to 
even begin in trying to diagnose what the problem is. So 
any pointers would be greatly appreciated.

David Priebe
Carnation, WA
91 200tqa 182k (his)
95.5 S6 114k (hers)
66 MGB 41k