Hey guys,

My 2000 Audi TT (base fwd 1.8 of course) heater is blowing luke warm air after the car warms up. After a while of driving the cabin gets decent (it's been 30-40 degrees outside lately). But something definitely isn't right, the heat out of the vents is never hot - not even warm. Here's what I know and what I've done so far:

What I know:

- Car heats up fine and temp gauge reaches and maintains center
- Blower fan is working (there is just one right?), air does come out of my vents
- I checked the diagnostics in the climate control unit, and 0 malfunction codes are returned.
- Also in the diagnostics of the climate control unit, when running 9c and 10c the values for the temperature regulator flap seem normal: if temp on system is set to "lo" it reports the flap is positioned in the low end (200s) and if on "HI" it reports in the high end (50s). This leads me to believe the computer at least thinks the temperature regulator motor is moving the flap into the correct position so perhaps it isn't bad.
- No engine codes
- Thermostat and Water pump (plastic prop, I know, dumb) were done about 2 years/50k miles ago with last timing belt
- I do not have VAGCOM

What I've done:

- Yesterday I did a complete coolant flush and also attempted to flush the heater core. I think I did it correctly - I removed the inlet and outlet hose after draining the system, hooked up some 3/4" hose and ran water through it in both directions from the hose. It came out clear, seemingly unrestricted and I did not see any debris or build up come out. So seemed fine.
- Today I disconnected the negative battery cable for about 10 minutes after reading it causes climate system and all motors to reset positions, which may help.
- Next today I took off the glove box thinking I might check the temperature flap motor anyway. Not sure if I got deep enough to see it or not and I have to go somewhere tomorrow so didn't want to completely tear the dash apart. I did spot two motors that seemed to be working just fine when I was playing with the temperatures from HI to Lo. I'm guessing they neither was the temperature regulator motor anyway since it's probably higher closer to the heater core, but at any rate here's a picture of them:

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Still no heat. Any ideas? Air trapped in core/getting in system? Inside of core built up and needs replaced? I'm lost, really do not want to go to the stealer-ship. Thanks in advance guys.

 

Find a way to make sure the blend door is going full sweep (temp control door) first. When the engine is hot and heater running, check the heater hoses. One should be hot, the other should be cooler. If they're both about the same temp, suspect heater core. The outlet should be cooler than inlet after giving up it's heat to the air going through the core. They can seemingly flow water fine but actually be 3/4 plugged up. I mean, if there's 12 tubes in the core, and 8 of them are plugged, water will still flow through the open 4 tubes pretty well but not transfer much heat.

Hope that makes sense. Kind of hard to explain this stuff with text on a web site.

 

Aspen, where is the blend door (temp control door)? Neither of the two motors in my pic aren't the blend motor right?

 

I'm fairly sure it's the one with the pink lever. Can't log in to Access Audi anymore (been 7 months since I was an Audi tech and I've been deleted). I can check tomorrow to be sure with the site we use at work. It's a professional subscription site and can't log in here at home.