Audi Repair: heater in audi not working, audi a6 quattro, flap valve

Question
heater in my 1997 audi a6 quattro is not blowing hot air. Mechanic has replaced water pump and thermostat and says heater core is working fine, but i only get heat for a few seconds when i rev my engine while in park. what else could be the problem? we even disconnected the fans because we thought they could be turning on to soon and not allowing engine to heat up enough, but that did not help.

Answer
If the heater core is warming up, then the heater valve should be working.  Then the flap valve control on the heater box is not working.  This is quite difficult to access, but there may be some experience with this out there on the forums.  I would see if soembody has a fix for this problem in the faq section of some of the forums.  Check also that both hoses to the heater core are hot.  Good luck,  Jan