Audi Repair: 96 a6 with no heat, rubber hoses, plastic vacuum

Question
My 1996 audi a6 has no heat.  No air come out of the top vents at all, and only cold air comes out of the floor vents.  I can increase the power of the air coming out, or turn it off completely, but i cant get hot air and i cant get air to come out of the vents which would warm or cool anything other than my feet.  I was wondering what you think the problem might be and how much it might cost to fix.  Thanks so much, whit

Answer
First make sure your radiator cooling fluid levels are all OK.  The usual culprit for this problem is either the heater matrix valve or the controller.  The valve is located in a rubber pipe, and is under the hood just behind the engine, it has a plastic vacuum line attached to it.  Check pretty much in the middle of the firewall behind the engine you should see two 3/4-1" rubber hoses going into the car side by side.  One of them will have a valve in it.  With the engine running and warm, have somebody control change the heater control from cold to hot and see if the valve position changes.  If it doesn't you can try to "persuade" it a little, but be careful these are made of plastic.  You can also feel both pipes, they should both be hot if the system is working.  If the pipes are not hot but the valve is working, then perhaps you have a blocked heater matrix, and this is a bigger problem.  Let me know what you find,  Jan.