Its going to be the thermostat, don't worry.

 

Jeez... still debating? It HAS to be the thermostat.. either bad or installed incorrectly. There is no other thing. Here's how I see 'new' stats going bad (as opposed to being bad outta the box, as suggested): New stat installed, coolant poured in, air pockets are still in the block. When the engine is started, said air pockets allow the coolant to flash to steam, steam get pushed to the stat, stat overheats and 'pops' open. This is a failsafe mode.

The 'air mixture flap' thing would be if ONLY the heat outta the vents cooled while moving. It set a CC code too, I know, mines zipped tied to 3/4 open as the servo is bad.

Sucks to have to do a job twice, but ..

 

Yep, There really is nothing else possible. I wasn't aware that the the mixture flap sets a code when it goes bad. Thermostat is where I was leaning in the initial post, but I am glad the thread stayed alive for the brainstorming though - maybe down the road it'll save someone some headache or doubts.

 

Did you try this because the flap would not be causing the needle to go down. The flap only relates to the heat inside the car.

I would take the T-Stat back and put in another new one. Either it is bad or it was installed improperly, and quite possibly upside down.



Note: that is some reallllllllllyyyyyy cold weather, you car might not like it!

 

Now that's something you just wouldn't think about. God I love sharing knowledge. Kinda like the time I was going nuts trying to figure out why a car was overheating until I sat down with a beer and noticed the bird feathers plastered over the front of the radiator.

 

Hey Imthedevil, what was the answer on this one? Just was looking for an update is all, thanks.

 

i just did the t stat on my 99 a4 same problem your having heat at idle no heat while moving.
before i change my t stat i read alot of forums on heat
what i found is alot of us have the same problem.
when i went to the local parts store the clerk ask me if i wanted a fail safe t stat. im like duh whats that. when they fail they fail open.
i said no thank u i put a stant 190 t stat in(wasnt fun but i like heat, call me a sissy if u want)
heat works great now
my opinon i think the audi oem t stat is weak by design, u might get a good one u might not,right out of the box,
i can't prove it
also i cheated when i fill the system back up.
fill the bottle open the bleed screws. one in front one in back of moter wait for fluid then close.
what i did after that is take the return line off of the heater core the( one with the weep hole)took a 10inch pieace of heater hose conected it to the heater core used a funnel an filled the heater core untill anti freeze comes out the open line, it takes a tone of air out of the system before u start the car.u still have to bleed the upper heater core line it just doesn't take as long


let me know if this helps u dave