Thanks for the reply... Now that I've gone thru past maintenance records on this car & the thermostat was replaced about 5k miles before I bought it... I'm not gonna even go down that road. I'll sell this thing before I pull the front end off again!

So, are you saying that even though my heater lines are both hot, that the core could still be clogged? I get no heat at any engine speed.

Also, I'm starting to have trouble with the air suspension & my torque converter. This car will be sold as soon as I can sell it... Any takers?

 

Same problem here (well, I get heat only when at >2K RPM) on my '01 A6 2.7T. Just curious why you need to do a core swap if it's blocked/clogged. Have you tried to do a flush similar to what's done in the tech article for an A4 (in the A4 "Engine" section, titled "Heater Core Flush"... sorry I can't link directly to it)? https://www.audiworld.com/tech/

I haven't done this yet, but I plan to and hopefully fix my issue. Maybe the flush only applies to the A4... let me know if I'm missing something here.

 

if both of your heater lines are hot when running the core is not clogged, not completely anyway.

I don't have time to search now but you can access diagnostic program on climate control by pressing some two buttons together, it will show you all temp sensors outputs etc which might be the issue with your car. If for example heaer core temp sensor is shut and shows cold all the time, the system will never enable heat. Just search the forums or even better google for this.

It is also possible that some output functions cam be acxtivated with vag-com/vcds so that you can determine what's not jiving in the system.

 

I would flush the core, then the engine before anything else. Be sure to properly bleed the system as you refill it. There are 2 bleed ports in the system. One is actually on the heater hose connection, can't remember inlet or outlet. You pull one of the hoses halfway off, and it will reveal a small hole that will allow air to escape as you fill it. The other is towards the front of the motor, next to the drivers side of the power steering pump. It's a pain to find.

One other trick is to remove the coolant res and lift it as high as possible when filling the engine. It adds a little more force to help remove air. Raising the front of the car may also help slightly.

Steve

 

Thanks. This is about where I'm at. I've been troubleshooting this all day & I'm at a loss. Everything I've checked is working good... I had a brain fart about the thermostat! It's been replaced before & judging by the fluid temp & other indications, it's working good. I finally bothered my mechanic & he also eluded to this button pushing method. I do not have a scanner or vag/com, so I'm doing this in the stone age. I'll do a search about this method, but at this point, I'm clueless.

 

Like I mentioned before, I've been posting about this ad nauseum and i have YET to find anyone who has reported a heater core temp sensor problem that was the cause of their no-heat condition, when reporting the same symptoms we all are. Again, if anyone comes across a cause OTHER than the core itself, please report it!

I have flushed my core myself six ways from Sunday, then had a shop flush it and the whole system, and bleed the **** out of it; and it STILL would not flow coolant in the correct direction; I had to swap hoses to get it to flow at all, and both of my hoses now are hot to the touch at the firewall, yet my heat at the defrosters and floor is warm at best. It WILL get hotter as the outside ambient temp rises, which only indicates that what hot air IS coming off the core by the blower motor isn't being cooled as fast as it travels thru the heater box.

I believe that the continued gunk that comes out with every flush indicates that the interior is coated with years-old coating, and is NOT ALLOWING HEAT-TRANSFER FROM THE COOLANT TO THE FINS, AND THEN TO THE BLOWER AIR. This is why the core feels hot at both hoses at the firewall, but no real heat into the cabin. You mechanical engineers that remember your heat-transfer classes from college check me on this.

I still stand by my inefficient heater-core theory, only really corrected by a core swap.

 

Brider, it sounds like your system might have a similar problem as mine. I would think that I would at least get some warm air, but I only get cold air. Period. I'm begining to wonder if my blend door is broken or jammed.

The system works perfectly as it should... It just blows cold air. For instance, if I set the system to "auto" it doesn't blow hard until the heater core warms up... Just as it should. If this didn't happen, I would suspect that the heater core wasn't getting warm enough, but it is. I've checked everything else, & I'm at a loss. The other problem could be a sensor somewhere???

I'm now trying to decide if I want to tear apart the dash to see if a blend door could possibly be jammed or broke. Or if there is a broke sensor... Quite honestly, I think I'll just bundle up for the rest of the winter... I've got bigger fish to kill.(torque converter!!!)

I'm seriously trying to figure out why in the hell this car is so popular. It's most definitely overrated.

 

I don't know anything about a "heater core temp sensor". If it does exost, I would have THOUGHT that the shop I took it to to FIX the no-heat condition would have checked it and confirmed to me that it was good.

My understanding was that on AUTO, the fan blower would begin to come on as the ENGINE temp came up, not the heater core temp. If that's the case, my theory about the heater core not transferring heat is still valid.

Good luck, let us know if you check the blend door motor.

Not to rub it in your face, but your TC problem is why I bought a 6-sp. Still, I'm no fan of constant shifting, I WISH I was driving an auto.

 

Well, I don't know anything about the sensor either... I'm just relaying information I've read. Your theory makes more sense. I'm gonna flush it tomorrow & see what happens. I wish I would've known more about the TC issue too, but my other car was wrecked & I got a descent deal on this one. Just FYI.

 

heater core & now I have heat. The mechanic said the likely cause was that somebody used the wrong coolant & it gums up the system... Really? I asked him about the temp of the in & out pipes on the heater core & his opinion was that they should be much hotter than they were.

I know that the manual says to use G12, but can this gummed up problem really happen? Or is it a corrosion issue? If anyone who has ever swapped a heater core has any insight, that would be some good info. To my knowledge, G12 is all that has ever been put in this car. The fluid looks about as orange as it could be. Anyhow, maybe it's the G12 that causes the problem!

Glad to finally have heat, although it's nowhere near as hot as it could be!