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AudiDoc, Independent Audi Shop Owner
Category: Audi
Satisfied Customers: 6457
Experience:  I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
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I have a HVAC problem with my 2001 A4Q. I'm not getting any

Customer Question

Hi Doc. I have a HVAC problem with my 2001 A4Q. I'm not getting any heat, though the AC works fine, and the blower works OK. I have been through the coolant bleeding procedure three times, the last time with my wife operating the accelerator to keep the engine running over 2000 RPM. Got a few bubbles, but not much. Just to clarify, the hose I loosened and partially pull off was the one on the passenger side of the two heater connections. My wild guess is that either the blend door that mixes the outside air and the heated air is not working properly, or one of the temp sensors in the duct work somewhere isn't working properly. I have the VAGCOM software from Ross installed on my laptop, but it is giving me SO much info that I don't know what to make of it. Please help! Thanks. Doug
Submitted: 10 months ago.
Category: Audi
Expert:  Wolfgang replied 10 months ago.

Thanks for choosing Just Answer . I'm Wolfgang here to help!!

I am confident we can resolve your problem together. Please
understand that I don't know your skill level. In most cases when you have a problem
with the way the vehicle performs, specialized tooling is required to acquire computer
data/information or engine testing results. We didn’t build these complicated vehicles; we
just diagnose and fix them. Also understand that I can't see, smell, hear, or touch the
vehicle either, so it may take a few replies to get to satisfactory results. Note there may be an issue where the complexity of the issue will require a Premium Service. This service will be an addition to the normal question cost. Usually it does not come down to this but keep in mind!! I am also going to direct you with the fastest, easiest and most common things to check first. Please be
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Below is my first answer or request for more information. If you do not understand it, or you need more information from me, or need me to go in more detail.

Very likely the heater core is clogged due to sediment collecting in the core till its to the top . there is a 15% chance that you may be able to flush it but this is a temp fix.

the correct procedure is to replace the heater core flush the cooling system with the heater core by passed 2 times then refill with new VW coolant at a 50/50 mix of coolant and water .

if you look at the pic that i have attached will explain futher why !!

anything else?

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Customer: replied 10 months ago.
Hello Wolfgang. Thanks for your reply. However, I have a long relationship with Audi Doc, and I had specifically requested him. Would you kindly forward this request to him. Thanks very much, and have a great day. Best regards, Doug
Expert:  AudiDoc replied 10 months ago.

Hey there, Doug. Been a while, and I'm also not on here nearly as much as I used to be. With that said, I do have to agree with Wolfgang on the heater core blockage. One thing you can do to rule out a blend door problem is to perform basic settings on them using vag-com/VCDS. First thing though, turn off your wireless on the laptop. Address 08 (HVAC) is seriously touchy, and the connection to it is a bit more stable without wireless on in most cases. So, select 08, then basic settings (04), and input 000. Allow all the fields to go from limit to limit, then stabilize. Takes maybe 30 seconds. Then they're set.

If this doesn't work, you can try to flush the core, but I'd go a step further. Disconnect both rubber hoses, use compressed air to blow all of the coolant you can out of the core, then fill it with CLR (you can get this at any grocery or hardware store). Let it sit for an hour, and then flush, backflush, flush, backflush.

Let me know how it goes

Customer: replied 10 months ago.
Hi Doc. Thanks so much for getting in touch with me. I just don't want to start looking for a really reliable Audi tech again. I had been through several that i was not very satisfied with before i found you. Please let me know how i can reliably reach you in the future, even if it takes several days to do so. Or if you really aren't going to be doing this online work anymore, I understand. Just let me know.But, since you did respond on this issue I assume you will guide me on this one. I will have a little time today or tomorrow to work on this. Family will taking up the holiday! I'll let you know i make out. Happy Thanksgiving!Doug
Customer: replied 9 months ago.
Hi Doc. Sorry about the delay in responding with results. Besides the holiday with family, I have had to deal with repairing a water/roof leak problem. Anyway, I have managed to get some lengths of the right size heater hose to work on this. I did drain and blow out the core, during which a small amount of tan colored sediment did come out. Then filled it with the CLR, let it sit for an hour and a half. They I flushed and back-flushed the core 8 times. Some small amount of additional tan sediment came out again, though I was surprised, and maybe a little disappointed at how little did come out. Then I reconnected the heater hoses, filled the coolant reservoir, and warmed up the engine. I then bled the heater core with my wife's assistance to keep the engine running at 2000 RPM for a few minutes. I then checked the air coming into the cabin when the temp was set to 80 deg. That procedure appears to have worked! Thanks so much for your help, as always. Take care, and have a great holiday. Also, for the future, how can I contact/request you without going through what I did this time? Or, if you are getting out of this Just Answer service, just please let me know. Take care. Doug
Expert:  AudiDoc replied 9 months ago.

Great to hear that it worked! So here's a suggestion. Do the same procedure again in a few weeks, and again a few weeks after that.

I do get notified immediately via email when I'm requested through the JA system, but I'm not logged in full time as I used to be, so no problems with future requests. Thanks for the report :-)

Customer: replied 9 months ago.
Hi. OK, thanks. I'll do that. And I will certainly request you for my future problems! Take care. Doug.
Customer: replied 9 months ago.
HI Doc. I am trying to rate your service at the top, but the site will not let me click on a star rating for some reason. But I'll keep checking back and maybe it will update that. Doug