Audi Repair: air conditioning heater, heater valve, audi a6

Question
Hi i recently bought an audi a6 estate 1998,i dont seem to be getting heat out of the unit i borrowed a friends unit that was working on his car but it still doesnt blow hot air out of mine any ideas please.

Answer
Well there could be a number of reasons for no heat.  Firstly check that the heater valve is working, this valve is located behind the engine, you will see two 1" hoses next to each other going into the car.  In one of these is a valve which is typically vacuum operated.  Have someone change the temperature in the car from hot to cold and see if the valve moves.  Also check that both hoses are hot...  Then the heater control module has to deflect air past the heater matrix, this is done from a control unit.  Which part did you exchange with your friend's unit?  Sometimes a coolant flush and clean also works.  Let me know,  Jan