... but it seems to either be flaps or thermostat or blower. I think it can't be the latter two because the AC works with the temp dial and I'm assuming it's pretty obvious if your blower has gone.

Just my two cents - but rather than guessing or depending on a local shop, it would be worth the 40-Euro to buy an OBDeleven OBDII diagnostic so you can run your own fault scans. Not just for this problem, but for any in the future. You don't need the Pro version, just the basic will suffice.

FAQ - OBDII Diagnostic Device Reviews

For the purpose of this discussion the term "OBDII Diagnostic Device" includes any diagnostic device that can be used to interrogate and report on the status of the electronic system of the Mk1, Mk2 or Mk3 TT by means of the OBD port. For the specific details on the differences between VCDS and...

www.ttforum.co.uk

 

Hi, As above, a fault scan required.
OBD Eleven well recommended on here.
Easy to use, cheap for Android users, a little more for iOS users.

OBDeleven device

Start conversation with your car

obdeleven.com

OBDeleven NextGen car diagnostic tool

OBDeleven NextGen is an easy-to-use OBD2 scanner for car diagnostics and customizations. Works for Volkswagen, Audi, BMW, MINI, Toyota, Lexus, and more.

obdeleven.com

Hoggy.

 

Thanks @Hoggy and @SwissJetPilot. I've ordered one now. 🙂 If I wanted to change some other coding, how much will that cost? I remember there was coding possible to change the mirrors to auto folding....

 

Once you have the OBDeleven, you should be able to engage features which are available for your particular year; e.g. needle sweep, mirror fold, etc. But only if these features are already programmed at the factory. Good read here on how to set up and use the OBDeleven -

FAQ - OBDeleven Open Box Review

I received my OBDeleven device this week with the Pro option package. The Pro just gives you a few more features and more credits up front. In retrospect, the Basic version (€39.99) would be just fine since you can pick up free credits for any of the one-touch apps you may want to implement. I...

www.ttforum.co.uk

 

BTW - this post in the Knowledge Base might come in handy -

https://www.ttforum.co.uk/threads/how-to-audi-tt-mk2-8j-hvac-blower-climate-control-problems-solutions.1786786/#post-8851338

 

BTW - this post in the Knowledge Base might come in handy -

https://www.ttforum.co.uk/threads/how-to-audi-tt-mk2-8j-hvac-blower-climate-control-problems-solutions.1786786/#post-8851338

Wow, awesome! Seems you're the right guy for the problem, thank you very much!

 

Well, not just me... The entire forum is a collection of experience and knowledge from other Forum members and various sources on the net. But I think you will find pretty much everything you'll need here.

Be sure you spend some time in the Knowledge Base and the Stickies as there's nuggets of goodness scattered about.

FAQ - Most Popular Links for Service, Maintenance and...

Here are some of the most frequently referenced "go to" links in the Mk2 Forum. These are intended for anyone who might have specific concerns or questions about what to look for when shopping for a Mk2 Coupe or Roadster. I've also included some of the more popular links covering recommended...

www.ttforum.co.uk

 

@SwissJetPilot @Hoggy The device has arrived (I paid extra to get it from amazon quicker... classic) - I'm getting two faults but neither related to this problem - just antenna issues due to a DAB radio connection, probably.

 

What are the fault codes...?

Did you run the fault diagnostic with the engine and AC running...?

------------------------------------------------------------------------------------------------
Going to park this info here while I run some Google searches and check my notes -

Address: 08-Auto HVAC (VCDS)
4B0-820-043-MY2.LBL

https://forums.ross-tech.com/index.php?threads/14456/

01206 - Signal for Duration of Ignition Off Time
00446 - Function Limitation due to Under-Voltage (Voltage: 10.00 V)


Control Unit: Air Conditioning 08 (OBDeleven)

 

Yep, AC coming back with no faults

 

You should see if you can blow the heater core out with some sort of flush, I used thoroflush on mine a few months ago and the air blows hot now. I had the exact same issue.

 

Damn it probably is the coolant. Even when I bought the car I said the coolant is a weird color. Apparently Audi always advised that "it could be changed but is really fine".

Hmmmm...

 

Given there are no fault codes against the AC address, then what jakob_b is recommending might be the way to go.

In fact, it would be worth having the coolant flushed and replaced. Audi says coolant is "lifetime" which is nonsense. I had mine done a few years ago, been fine since. Generally it's recommended around 50,000 miles, but of course there are those who recommend it be done more often. Fluid and coolant changes are cheap insurance.

 

@SwissJetPilot @jakob_b

I'm on the fence whether to just have the coolant flushed (cheap 45 pound job) or if I need to try and get to the heater matrix flushed too (probably myself as I'm a cheapskate). Some even replace it completely:

.

I hope I wouldn't have to remove the matrix? Rather just connect to the hoses and pump through thoroflush mixture? What would I need to be able to do that though? I don't have a vacuum pump thingy. Also, must the coolant all be drained out before I do that? Probably? Sorry...

 

@SwissJetPilot @jakob_b

I'm on the fence whether to just have the coolant flushed (cheap 45 pound job) or if I need to try and get to the heater matrix flushed too (probably myself as I'm a cheapskate). Some even replace it completely:

.

I hope I wouldn't have to remove the matrix? Rather just connect to the hoses and pump through thoroflush mixture? What would I need to be able to do that though? I don't have a vacuum pump thingy. Also, must the coolant all be drained out before I do that? Probably? Sorry...

I used my mouth to be honest lolll just went to the hardware store and bought 2 3 foot hoses probably like 2 inch diameter (I don’t fully remember the size sorry) and tightened them on with hose clamp then dumped the mixture into the matrix and left it for about 10 mins and literally blew it out with my mouth it took quite a lot of effort but we got pretty much everything out id definitely recommend that instead of replacing it or alteast trying it first. it’s pretty hard on the tt. I didn’t even fully flush my coolant I just added more for the stuff I lost removing the hoses which was like a litre.

 

Also no you don’t need to drain the coolant first

 

Since you have to disconnect the heater core lines to flush it, you will likely introduce air into the system which needs to be removed. The air might work it's way out through the system on its own, but it could also get trapped and cause other issues.

If doing a DIY heater core and system coolant flush/replacement isn't your cup of tea, you might ask the service techs if they would flush the heater core first, and then do a complete system flush and coolant replacement.

Personally, I would have it all done at one go by someone who has all the equipment and be done with it. Just my two cents.

Here's a link to the Workshop Manuals if you need a reference. Look for this one: HVAC, Heating Ventilation & Air Conditioning - RG 80 87 - D3E80068107

 

I used my mouth to be honest lolll just went to the hardware store and bought 2 3 foot hoses probably like 2 inch diameter (I don’t fully remember the size sorry) and tightened them on with hose clamp then dumped the mixture into the matrix and left it for about 10 mins and literally blew it out with my mouth it took quite a lot of effort but we got pretty much everything out id definitely recommend that instead of replacing it or alteast trying it first. it’s pretty hard on the tt. I didn’t even fully flush my coolant I just added more for the stuff I lost removing the hoses which was like a litre.

ALSO I’d highly recommend a couple of large buckets for coolant to drain into and the flush mixture cuz i didn’t and it went literally everywhere lol I was cleaning for a while

Since you have to disconnect the heater core lines to flush it, you will likely introduce air into the system which needs to be replaced. It might work it's way out through the system, but it could also get trapped and cause other issues.

If doing a DIY heater core and system coolant flush/replacement isn't your cup of tea, you might ask the service techs if they would flush the heater core first, and then do a complete system flush and coolant replacement.

yeah definitely a good point I ran the car with the coolant cap off for like 20 mins after just to see if any air was introduced but definitely a good idea to do it in a more pro way if you love your car a lil more butttt I’ve put like 3000 more km on and mine has been completely warm and fine but definitely a good idea to go pro.

 

Some additional info on heater cores from Charles the Humble Mechanic -

After you do the first flush of the core and get the bulk of whatever debris is in there out, you can pour this in, and let it sit for while, and then flush it again. It's designed to flush the entire system, but you can use it to just clean the core too.

 

Thanks again guys @jakob_b @SwissJetPilot

My garden hose doesn't even remotely reach the car parking, so that wasn't an option. I instead just used warm water and some cooling system flush to get out debris, blowing it out (and letting the flush sit for 10 min) eventually it was all clear. A lot came out, bits of sandy looking nonsense and what not. About the same or a bit more as I've seen in the videos I've watched.

I then refilled with coolant mix, reconnected the pipes (which were actually bloody hard to get on) and started the car, topping up coolant with the cap open. I then took the car for a 15 minute relateively spirited drive, but in the end, maybe it's 3 degrees warmer at best...

Edit: perhaps bleeding the core is needed, as all i did was fill it with liquid but I'm thinking that was perhaps not good enough.It's dark here now so that's a job for tomorrow. Is there a bleeder hole on the top pipe? I didn't notice it today.

 

Yeah that’s what I tried as the very first thing and I had the same issue where it wasn’t much warmer but after a flush with some cleaner it should be better

 

Did you try flushing in both directions...?

 

Yep I did...

 

@ Arnedk - If and when you flush the core again, can you take some pictures of the process and post them here in the Forum? it would be interesting for anyone else that wants to do this so they can see what's involved.

 

If it helps I have some photos

 

@ jakob_b - Thanks! Actually if you had some closer shots of removing the connectors and how you put on the clear flush lines, that would be really helpful.

Are the connectors difficult to remove...?

It looks pretty straight forward, just use a screwdriver to lift the metal retaining clip to release it...?

I researched the actual parts to get a better understanding of what you guys are working with. And from the photos shown below I noticed both the male and female connectors are keyed, meaning one should not attempt to rotate it.

Both the upper and lower connectors just pull straight off. Is this also correct...?

 

Are the connectors difficult to remove...? It looks pretty straight forward, just use a screwdriver to lift the retaining clip to release it...?

I also noticed it is keyed, meaning one should not attempt to rotate it. It just pulls straight off. Is this correct?

View attachment 511734
View attachment 511738

That's how one would assume they work but even after the clip is in the open position, pulling the actual thing off (straight) takes a lot of effort. Then getting it back on is the same story. Not sure if I'm doing it wrong. Perhaps @jakob_b can comment on his experience.

 

@SwissJetPilot @jakob_b

I've re-done the job today with the help of my friendly neighbors again. Bought a hosepipe and blasted it both ways, had product in there for a good 15-20 minutes, moving it back and fourth in the system for some time. In the end, mostly it seems in vain, as the heater is again 5 degrees warmer than it was before, or maybe less. We took a few photos but they're on my phone - I'll add them later. For now I'm a bit miserable that despite all the effort and expense, the car is uncured...

Could it be the thermostat? Or some other part? If so, why wouldn't it flag up an error code?

A mechanic suggested I leave the coolant cap off tonight, but I think the system is self clearing for any airlocks anyway, right? Or should I do it still?

Anyway

 

sorry to hear that your car only a lil warmer I imagine your heater core is just extremely gunked up or something like that my heat in my car isn't amazing for sure and I've heard around that tt's and golfs kinda suffer from lack of heat from the factory sometimes but idk it works for my Canadian climate and mine sure got hotter than that when I did my flush so I would maybe consult a mechanic at this point ask if there's any more you can do. but if you wanna try again maybe just continue flushing it until everything is removed i did mine like 4 times before everything was removed but it does totally get annoying having to take the intake pipes off and such over and over again.

 

I've watched the below video to understand where to feel for something heating up. Maybe a good test for the thermostat.

 

@SwissJetPilot @jakob_b

I've re-done the job today with the help of my friendly neighbors again. Bought a hosepipe and blasted it both ways, had product in there for a good 15-20 minutes, moving it back and fourth in the system for some time. In the end, mostly it seems in vain, as the heater is again 5 degrees warmer than it was before, or maybe less. We took a few photos but they're on my phone - I'll add them later. For now I'm a bit miserable that despite all the effort and expense, the car is uncured...

Could it be the thermostat? Or some other part? If so, why wouldn't it flag up an error code?

A mechanic suggested I leave the coolant cap off tonight, but I think the system is self clearing for any airlocks anyway, right? Or should I do it still?

Anyway

sorry to hear your cars only slightly warmer my car definitely doesn't have he greatest heating and I've heard from others that some of those cars and golfs suffer the same crappy heating from the factory but mine got much warmer when I did my original flush but I did do mine like 4 times in total tho, I used almost an entire bottle of thoroflush and by the end there was still tiny particles coming out so It very well could be that there still is build up from old coolant in the heater core at least

sorry to hear that your car only a lil warmer I imagine your heater core is just extremely gunked up or something like that my heat in my car isn't amazing for sure and I've heard around that tt's and golfs kinda suffer from lack of heat from the factory sometimes but idk it works for my Canadian climate and mine sure got hotter than that when I did my flush so I would maybe consult a mechanic at this point ask if there's any more you can do. but if you wanna try again maybe just continue flushing it until everything is removed i did mine like 4 times before everything was removed but it does totally get annoying having to take the intake pipes off and such over and over again.

that's about all I could imagine I really don't think you would replace your matrix unless its like actually damaged which at that point it would be noticeable in that your car would probably smell like coolant in the cab, I've also seen something about a silica bag Audi used to put in some of their cars in the actual coolant ball to expand the "coolant life 🤪" idk if it applies to the later gen mk2 tts because my car didn't have it but apparently that can release silica into the coolant system which damages the heater core and water pump and can also make the heat really weak but that's more obvious in that your cars also overheating so maybe look into that tho probably isn't the case here but just pointing it out. also just wondering how much gunk came out on your flush? because I had like probably an oil drain pan worth of just old build-up on the fins in the matrix id just say keep on flushin

 

sorry to hear your cars only slightly warmer my car definitely doesn't have he greatest heating and I've heard from others that some of those cars and golfs suffer the same crappy heating from the factory but mine got much warmer when I did my original flush but I did do mine like 4 times in total tho, I used almost an entire bottle of thoroflush and by the end there was still tiny particles coming out so It very well could be that there still is build up from old coolant in the heater core at least
that's about all I could imagine I really don't think you would replace your matrix unless its like actually damaged which at that point it would be noticeable in that your car would probably smell like coolant in the cab, I've also seen something about a silica bag Audi used to put in some of their cars in the actual coolant ball to expand the "coolant life 🤪" idk if it applies to the later gen mk2 tts because my car didn't have it but apparently that can release silica into the coolant system which damages the heater core and water pump and can also make the heat really weak but that's more obvious in that your cars also overheating so maybe look into that tho probably isn't the case here but just pointing it out. also just wondering how much gunk came out on your flush? because I had like probably an oil drain pan worth of just old build-up on the fins in the matrix id just say keep on flushin

My car doesn't have the gel stuff, I've heard of that weird thing though...

I will use my thermostat to check how hot the air gets.

Damn, 4 flushes... agh... lol.

Guys, how many L is the entire system? Maybe because of how cold it is the heater core isn't ever able to break up the nonsense properly, ideally it should be running, right? But for that I would need to flush the whole cooling system...

 

I guess the next question would be are you getting a good flow through the heater core?

If not, then it's probably really blocked and requires some additional attempts.

If you haven't done so already, it might be worth blowing out all the coolant that's in it so it's completely void of any coolant, and then fill it with the coolant flush/cleaner solution and let it sit for 30 minutes or so and then flush it again.

While it is possible to DIY a heater core replacement, it does not look easy, at least from the YouTube videos I have reviewed. Personally, I would make every possible effort to verify the core is actually clear before going that route.

However if flow is good, then it might be something else like the thermostat.

 

I guess the next question would be are you getting a good flow through the heater core?

If not, then it's probably really blocked and requires some additional attempts.

If you haven't done so already, it might be worth blowing out all the coolant that's in it so it's completely void of any coolant, and then fill it with the coolant flush/cleaner solution and let it sit for 30 minutes or so and then flush it again.

While it is possible to DIY a heater core replacement, it does not look easy, at least from the YouTube videos I have reviewed. Personally, I would make every possible effort to verify the core is actually clear before going that route.

However if flow is good, then it might be something else like the thermostat.

The flow is not bad. It's not exactly super smooth blowing coolant/air through it, but the pipes which were attached were not ideal and had some kinks in it, so that's probably the kickback I felt. Honestly though it felt like it was quite smooth running. Would water need to go through the whole rad to flow, or could it be that it's flowing well only through part of the rad?

I did leave the cleaner inside for 15 min the day before yesterday, and then yesterday again.

Thoroflush is hard to get in the UK, so I used what's in the auto shop. These two: Holts Speedflush 250ml | Halfords UK and Wynns Radiator Flush | Halfords UK - maybe they are crap products, but they've got good reviews on Amazon.

 

Sounds like you have done all you can at this point. I wouldn't discount having a complete coolant flush done, but not sure that will necessarily resolve this issue. However coolant, like oil, should be replaced routinely, between 30k-50k miles or every five years or so.

The only other thing I can think of is to visually check that the temperature control flap is actually working. I know a fault scan should have detected a failure, but if you can actually observe it moving as it should, you can take the off the list of possible causes for low heat before you start seriously considering a core replacement.

Also this from another VAG forum -

• Check if the input and the output pipes to the matrix are equally hot?

If so it is not blocked.​

• Is the temp gauge getting up to 88/90 C°?

If so then this may be a flap control motor failure or the car compartment sensor is and telling the heater the car is hot enough.​

• If you select A/C on does it blow cold air in the believe it is already to hot.

If so, then the sensor may be bad.​

• Is the water in your header tank a clear pink colour?

If not, then the coolant should be flushed and replaced.​

While the fault scan should detect a bad servo or sensor, it wouldn't hurt to visually inspect the flap servo and see if it is actually working when you make a change with the Climate Control knob. It's possible, although unlikely, it somehow came off the control arm and only the servo is moving, but the flap is stuck.

I would verify every possible cause before resorting to exchanging the heater core.

1. Low coolant or air in the cooling system
2. Clogged heater core
3. Bad thermostat
4. Bad water pump
5. Faulty blend door actuatorBad water pump
6. Dirty cabin air filter
7. Sluggish or dead blowerblower motor
8. Faulty HVAC module

https://www.wheelsjoint.com/audi-tt-heater-not-working-causes-and-diagnosis/#:~:text=You%20don%E2%80%99t%20have%20to%20remove%20the%20heater%20core,is%20cold%2C%20you%20have%20a%20plugged%20heater%20core

.

 

Sounds like you have done all you can at this point. I wouldn't discount having a complete coolant flush done, but not sure that will necessarily resolve this issue. However coolant, like oil, should be replaced routinely, between 30k-50k miles or every five years or so.

The only other thing I can think of is to visually check that the temperature control flap is actually working. I know a fault scan should have detected a failure, but if you can actually observe it moving as it should, you can take the off the list of possible causes for low heat before you start seriously considering a core replacement.

Also this from another VAG forum -

• Check if the input and the output pipes to the matrix are equally hot?

If so it is not blocked.​

• Is the temp gauge getting up to 88/90 C°?

If so then this may be a flap control motor failure or the car compartment sensor is and telling the heater the car is hot enough.​

• If you select A/C on does it blow cold air in the believe it is already to hot.

If so, then the sensor may be bad.​

• Is the water in your header tank a clear pink colour?

If not, then the coolant should be flushed and replaced.​

While the fault scan should detect a bad servo or sensor, it wouldn't hurt to visually inspect the flap servo and see if it is actually working when you make a change with the Climate Control knob. It's possible, although unlikely, it somehow came off the control arm and only the servo is moving, but the flap is stuck.

I would verify every possible cause before resorting to exchanging the heater core.

1. Low coolant or air in the cooling system
2. Clogged heater core
3. Bad thermostat
4. Bad water pump
5. Faulty blend door actuatorBad water pump
6. Dirty cabin air filter
7. Sluggish or dead blowerblower motor
8. Faulty HVAC module

https://www.wheelsjoint.com/audi-tt-heater-not-working-causes-and-diagnosis/#:~:text=You%20don%E2%80%99t%20have%20to%20remove%20the%20heater%20core,is%20cold%2C%20you%20have%20a%20plugged%20heater%20core

.

Thanks for all the tips, will run through and report back. One thing: what do you mean is the temp gauge getting to 90c? Wouldn't that just mean it's doing as it should?

Edit: also, how much of the car will I need to tear up to see if the flap isn't working/stuck?

 

From what I have read on VAG platform vehicles, the easiest test for a blocked core (matrix) is comparing the temperature difference between the upper vs. lower hose. If there's a significant difference, then odds are good it's blocked or at least partially blocked. As far as I am aware, the heater core in the Mk2 TT is always getting coolant going through it, unlike some vehicles which have a shut off valve.

IMHO continued attempts at unblocking it are really your best bet at this point given everything else seems okay. If you have lots of plastic tubing and and some valves lying about your work shed, you could go all out like this guy. He mentions using CLR, which is Calcium, Line and Rust Remover which is quite common in the US and Canada. I would suspect you guys have something similar like ZEP (Amazon link here). Just be sure whatever you use won't attack aluminum!

To check the vent servos on the HVAC box, you'll want to remove the glove box and the knee panel below the steering wheel. Just be aware of any electrical connectors as you remove them.

Those are relatively easy to do remove and will give you the best opportunity to see the servos without getting too far into a major disassembly. A good LED flashlight will come in really handy. It might also be easier with two people, one doing the observation, the other turning the climate control knobs.

I'm not 100% sure, but believe you might also be able to see them if you remove all three center vents, I would start there since they are very easy to remove - you'll now soon enough.

Just be sure to remove them correctly as shown below or you will damage them. Do not attempt to rotate the vent itself, as it is keyed. Only rotate the outer bezel to get the gears lined up and out of the way before pulling it straight out.

For reference, take a look through Workshop Manual General Body Repairs, Interior - RG 68 69 70 72 74 - A005TT00420. You can download it from the KB.

See this link to give yourself an orientation of the HVAC box and where the vent servos are located. I believe the one shown is for LHD, and a RHD would be most likely be reversed.

 

From what I have read on VAG platform vehicles, the easiest test for a blocked core (matrix) is comparing the temperature difference between the upper vs. lower hose. If there's a significant difference, then odds are good it's blocked or at least partially blocked. As far as I am aware, the heater core in the Mk2 TT is always getting coolant going through it, unlike some vehicles which have a shut off valve.

IMHO continued attempts at unblocking it are really your best bet at this point given everything else seems okay. If you have lots of plastic tubing and and some valves lying about your work shed, you could go all out like this guy. He mentions using CLR, which is Calcium, Line and Rust Remover which is quite common in the US and Canada. I would suspect you guys have something similar like ZEP (Amazon link here). Just be sure whatever you use won't attack aluminum!

To check the vent servos on the HVAC box, you'll want to remove the glove box and the knee panel below the steering wheel. Just be aware of any electrical connectors as you remove them.

Those are relatively easy to do remove and will give you the best opportunity to see the servos without getting too far into a major disassembly. A good LED flashlight will come in really handy. It might also be easier with two people, one doing the observation, the other turning the climate control knobs.

I'm not 100% sure, but believe you might also be able to see them if you remove all three center vents, I would start there since they are very easy to remove - you'll now soon enough.

Just be sure to remove them correctly as shown below or you will damage them. Do not attempt to rotate the vent itself, as it is keyed. Only rotate the outer bezel to get the gears lined up and out of the way before pulling it straight out.

For reference, take a look through Workshop Manual General Body Repairs, Interior - RG 68 69 70 72 74 - A005TT00420. You can download it from the KB.

See this link to give yourself an orientation of the HVAC box and where the vent servos are located. I believe the one shown is for LHD, and a RHD would be most likely be reversed.

View attachment 511773
View attachment 511774

Thanks for all this info! I'll pull some vents and take a look back there, that should be easy enough with this guide. ZEP looks like some nice tough stuff, but it does contain phosphoric acid, which is used to "shine" aluminium - I suppose it's slightly reactive? Hmmm...