On my 2001 a4 1.8t, when I turn on heat it goes on for about 2 sec then cold air comes out, it is not the heater core(i think) it has some thing to do with the valve that controls the heat, does any one know where it is located? or what could it be?

 

there is a valve in the IN hose going to the heater core which is at the back of the engine. but how do you know the core isn't clogged?

 

well, coolant definitely isn't running through your core....sounds like a clog somewhere....

like chaos asked, how do you know the clog isnt in your core?