I just recently purchase my first Audi. I flew from Omaha to Dallas a couple weeks ago after being reassured everything was working perfect on the car. Needless to say it didn't take long to figure out the heater wasn't working as it should. I have spent hours searching the forums and came across some good info, just looking for a little more at this point.

2001 Audi A4 avant, 1.8t with 160k miles. I do not have access to a vagcom to run for codes. Other than heater issue, only known issue is recently outside temp has been way off and fluctuating, it was not doing this a week ago...

Initial Symptoms-
After car was warmed up and coolant gauge directly in the middle (never fluctuates thereafter)
At Idle - Cold
Under throttle - barely warm

Last weekend I ran water through the heater core, in both directions, about 10 min of flushing each direction, a good amount of small white particles came out. Blew out the water under my own breath, Added coolant/ distilled water.

Results
After car was warmed up
Idle - barely warm
Under throttle - hot air (but only in middle dash vents, air on the floor is only slightly warm)

Describing this to a friend who is a lead mechanic at a large ford dealership said his best guess was heater core issues still, that at idle there isn't nearly as much flow through the heater core.

I have no desire of taking the dash out and replacing, so I was thinking of doing the flush again, but this time allowing CLR to soak for a few hours as well.

Any thoughts or help is greatly appreciated. Thanks.

 

Do the CLR method and you should be good. You've already made progress with the heat. On these Audi's the heater core is the highest point in the cooling system, as you've probably read, also, it is a 'passive' system, meaning there is only the water pump. Every Audi I've ever owned, when at idle, heat is warm/hot, but NOT as hot as when under throttle.

As far as your vents and floor vents, there maybe a vent motor/flap not working properly, since you don't have a VAG, the heating/cooling system has it's own diagnostics built in - you can search the forums and there is some DIY on how to access them right off the panel, I don't remember off the top of my head how to access them. But, it will show you all kinds of results and codes as well.

 

After 2 CLR flushes, 1st left in for about 45 min, second left in for about 90 minutes, both times had quite a bit of small white particles.

Hooked up a snap-on code reader and found 3 codes
00787 - Temp sensor in fresh air intake duct (G89) open circuit/short with power
01272 - Central Air Flap Motor - V70 blocked or no voltage-intermittent
01206 - Signal for duration of ignition off time not a pluasible signal intermittent

Cleared the codes and ONLY 00787 came on.

RESULTS - Hot air during idle, hot air on floor vents..... Success

 

Now I just have two other issues to tackle

1 - Learn how to take the front bumper off it appears to replace the driver side turn signal

2 - rear windshield washer line is leaking under drivers door, so need to figure out where leak is exactly, then how to pull the line out while pulling the new one through.

 

It is possible to remove the headlamp assembly on the one-piece unit where the turn signal is part of the headlamp without removing the bumper.

If you plan on doing the maintenance and repair on this vehicle, it would be best to obtain the Bentley workshop manual, which outlines many of these procedures. You can also search this forum for a write up on changing the headlamp and turn signal bulbs.

 

Congrats! For sure you are using pink antifreeze right? Should be able to replace the turn signal bulb without pulling the bumper but pulling the bumper is pretty easy. +1 to HBAudi on finding a Bentley manual and google is your friend too. Nebraska winter and no heat? I remember that. Grew up in Fremont.