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Discussion Starter · #1 · (Edited)
This write up presents a way to access the blend doors on a MK1 Audi TT without removing the entire dash. The blend doors have foam coverings that are often deteriorated causing bits of foam to blow out of the vents and decreased heat and cooling output due to improper blending of hot and cold air. The blend doors are located behind the radio cage and feed two ducts that go into the two center dash vents. In order to get at them, the glovebox, driver side lower dash, and the entire center section have to come out. The center piece can only be removed last as one mounting location is blocked on each side by the glovebox and lower dash. Removal of these two are somewhat similar. For a quick description you can read the following sections, or skip ahead if you’ve removed these panels before.

*Disclaimer: Some parts of this job can be a bit difficult, especially for those with larger hands, so be sure to read ahead before starting disassembly. The purpose of this write up is to show how I chose to address this issue, anything you do to your car is on you so proceed carefully, don’t do anything you wouldn’t do.

Glovebox:
Note – As you remove screws make sure to support the glovebox as needed so it doesn’t fall or break any of the plastic mounting points under its own weight.
Same with reinstall.

First remove the two screws that are in the top of the lower glovebox tray in the footwell. Pry off the panel that covers the end of the dash on the passenger side. In there, you’ll find a bunch of interior screws. Only some of them need to be removed.

58536

Then open the glovebox and remove the screws located at the top going straight up toward the dash, make sure you’re holding it up because these are the last ones. Lower it slightly and disconnect all the electrical things. There’s a long tab that slides behind the inner dash end panel and a metal panel inside (confusing…pictured below).

58537

Pay attention to this tab, you may have to help guide it out. The glovebox should come straight out or it may require a special touch, either way just be careful of all tabs and don’t force anything. Not a bad time for latch repairs.

Lower Dash:
This is a bit easier than the glovebox. Remove the panel that covers the fuse box. Just like the other side, only some screws in here need to be removed. Also remove the 2 screws underneath in the footwell. The lower dash has two press fit mounts at the top near the cluster, they look like this

58538

Carefully pull the upper edge of the panel forward and they should just pop out. This panel also has the same long tab that slides behind what’s now the fuse panel. You can then free the OBD2 port from the panel, this is some sort of clip in fit, take a good look at it and you should be able to release it by pressing in a couple tabs. Disconnect the headlight switch as well.

Also remove the two small panels on the inside of each footwell, there should be two screws in each, with the front one underneath a little plastic cover.

Radio Cage:
First remove the knee bars.
The ash tray has one screw at the top when you open it. Remove that, and then pull it forward with a slight jiggle to remove.
Using the correct radio keys, pull out and disconnect the radio.

You can then remove the outer plastic trim, which has two screws behind where the radio used to be, and one way underneath behind where the ashtray used to be. Pulling this off will reveal the screws for the HVAC controls. Remove and disconnect them as well.
All that should remain is the plastic cage with the aluminum radio door. There is a screw on each side that goes straight up into the dash, only 1 of 2 are pictured

58540

And there are 2 more underneath the cage.
Make sure all the wires are free when you pull the cage and be sure not to scratch the radio door. Now it should just be you, your heater box, and some wires. You’ll see the two ducts that go into the center dash.

58542

First unclip the wires that are tied down onto the small plastic piece. This piece also has one screw on each side as you can see in the next picture. Remove both screws…you will not be able to remove the whole piece yet, but its pictured for clarity.

58543

You’ll then need to remove this metal piece from the passenger side where the knee bars bolt up in order to make some room for the ducts to move slightly.

58544

Now remove the staples that hold the ducts to the plastic piece. They are on all 4 sides of each outlet (some may have fewer). I straightened out the staple legs and pushed them inside so I could pull the ducts off. You can see one of the staples here.

58545

This one has the legs coming out, some may have the legs going in, those can just be pulled out. This is one of the more difficult parts as the staple on the top side of the top duct (if you have one) is not easy to get to and cannot be seen. You’ll need some kind of pick or long small screwdriver for this. It requires a lot of jostling and squeezing of the ducts, but with some finesse you’ll get them off and be glad to see the infamous blend door…or at least one of them.

58546

After pulling off both ducts, the plastic piece sandwiched between can come out and you’ll see the whole blend door. The ducts have enough play so that the dash vent ends do not need to be disconnected. As pictured above, the door is closed (or open…whatever) but you can plug your HVAC controls back in and play with them until it opens up, granting you access to the second, deeper blend door.

58547

Just scoop out many handfuls from in between the doors and pull off any remaining doodoo foam clinging on to haunt you for another 20 years.

I chose to use HVAC aluminum foil tape to recover my doors, laying horizontal strips over the holes. I tried my best to neatly wrap them around both sides of the door so that there wouldn’t be an exposed sticky side. It’s up to you how particular to be here, but anything is better than the sorry state they’re likely in. Just try to do the cleanest job possible and don’t put tape anywhere it could interfere with the movement of the doors. HVAC tape is really sticky so position the strips carefully and slowly. Once you’re happy…job done. Fiddle with the HVAC controls to test door movement.

Refit the sandwiched plastic piece and press the ducts back into place. You can try to refix them with a staple gun or however you like. They fit pretty snug just slipped back over the lips but refixing is up to you.

Interior reassembly is the reverse. Enjoy better heat and finally an end to the foam blowing out of your vents.


I was also able to design a solution here that is a bit more graceful than covering the doors with HVAC foil tape. That’s how I fixed mine initially and trust me it’s not so easy reaching in and neatly applying really sticky tape, especially for those with large hands. I’ve designed some 3D printed ABS plugs that fit directly into the cutouts of the doors. They snap right in and seal the door completely which should restore the correct mix ratios that the unit thinks it’s achieving. ABS is known to withstand temperatures much higher than what is achieved in the HVAC unit. They definitely make the job much easier and give a nice clean result. If you’re interested, drop me a message and I’ll get you setup.


 

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This write up presents a way to access the blend doors on a MK1 Audi TT without removing the entire dash. The blend doors have foam coverings that are often deteriorated causing bits of foam to blow out of the vents and decreased heat and cooling output due to improper blending of hot and cold air. The blend doors are located behind the radio cage and feed two ducts that go into the two center dash vents. In order to get at them, the glovebox, driver side lower dash, and the entire center section have to come out. The center piece can only be removed last as one mounting location is blocked on each side by the glovebox and lower dash. Removal of these two are somewhat similar. For a quick description you can read the following sections, or skip ahead if you’ve removed these panels before.

*Disclaimer: Some parts of this job can be a bit difficult, especially for those with larger hands, so be sure to read ahead before starting disassembly. The purpose of this write up is to show how I chose to address this issue, anything you do to your car is on you so proceed carefully, don’t do anything you wouldn’t do.

Glovebox:
Note – As you remove screws make sure to support the glovebox as needed so it doesn’t fall or break any of the plastic mounting points under its own weight.
Same with reinstall.

First remove the two screws that are in the top of the lower glovebox tray in the footwell. Pry off the panel that covers the end of the dash on the passenger side. In there, you’ll find a bunch of interior screws. Only some of them need to be removed.

Then open the glovebox and remove the screws located at the top going straight up toward the dash, make sure you’re holding it up because these are the last ones. Lower it slightly and disconnect all the electrical things. There’s a long tab that slides behind the inner dash end panel and a metal panel inside (confusing…pictured below).

Pay attention to this tab, you may have to help guide it out. The glovebox should come straight out or it may require a special touch, either way just be careful of all tabs and don’t force anything. Not a bad time for latch repairs.

Lower Dash:
This is a bit easier than the glovebox. Remove the panel that covers the fuse box. Just like the other side, only some screws in here need to be removed. Also remove the 2 screws underneath in the footwell. The lower dash has two press fit mounts at the top near the cluster, they look like this

Carefully pull the upper edge of the panel forward and they should just pop out. This panel also has the same long tab that slides behind what’s now the fuse panel. You can then free the OBD2 port from the panel, this is some sort of clip in fit, take a good look at it and you should be able to release it by pressing in a couple tabs. Disconnect the headlight switch as well.

Also remove the two small panels on the inside of each footwell, there should be two screws in each, with the front one underneath a little plastic cover.

Radio Cage:
First remove the knee bars.
The ash tray has one screw at the top when you open it. Remove that, and then pull it forward with a slight jiggle to remove.
Using the correct radio keys, pull out and disconnect the radio.

You can then remove the outer plastic trim, which has two screws behind where the radio used to be, and one way underneath behind where the ashtray used to be. Pulling this off will reveal the screws for the HVAC controls. Remove and disconnect them as well.
All that should remain is the plastic cage with the aluminum radio door. There is a screw on each side that goes straight up into the dash, only 1 of 2 are pictured

And there are 2 more underneath the cage.
Make sure all the wires are free when you pull the cage and be sure not to scratch the radio door. Now it should just be you, your heater box, and some wires. You’ll see the two ducts that go into the center dash.

First unclip the wires that are tied down onto the small plastic piece. This piece also has one screw on each side as you can see in the next picture. Remove both screws…you will not be able to remove the whole piece yet, but its pictured for clarity.

You’ll then need to remove this metal piece from the passenger side where the knee bars bolt up in order to make some room for the ducts to move slightly.

Now remove the staples that hold the ducts to the plastic piece. They are on all 4 sides of each outlet (some may have fewer). I straightened out the staple legs and pushed them inside so I could pull the ducts off. You can see one of the staples here.

This one has the legs coming out, some may have the legs going in, those can just be pulled out. This is one of the more difficult parts as the staple on the top side of the top duct (if you have one) is not easy to get to and cannot be seen. You’ll need some kind of pick or long small screwdriver for this. It requires a lot of jostling and squeezing of the ducts, but with some finesse you’ll get them off and be glad to see the infamous blend door…or at least one of them.

After pulling off both ducts, the plastic piece sandwiched between can come out and you’ll see the whole blend door. The ducts have enough play so that the dash vent ends do not need to be disconnected. As pictured above, the door is closed (or open…whatever) but you can plug your HVAC controls back in and play with them until it opens up, granting you access to the second, deeper blend door.

Just scoop out many handfuls from in between the doors and pull off any remaining doodoo foam clinging on to haunt you for another 20 years.

I chose to use HVAC aluminum foil tape to recover my doors, laying horizontal strips over the holes. I tried my best to neatly wrap them around both sides of the door so that there wouldn’t be an exposed sticky side. It’s up to you how particular to be here, but anything is better than the sorry state they’re likely in. Just try to do the cleanest job possible and don’t put tape anywhere it could interfere with the movement of the doors. HVAC tape is really sticky so position the strips carefully and slowly. Once you’re happy…job done. Fiddle with the HVAC controls to test door movement.

Refit the sandwiched plastic piece and press the ducts back into place. You can try to refix them with a staple gun or however you like. They fit pretty snug just slipped back over the lips but refixing is up to you.

Interior reassembly is the reverse. Enjoy better heat and finally an end to the foam blowing out of your vents.


I was also able to design a solution here that is a bit more graceful than covering the doors with HVAC foil tape. That’s how I fixed mine initially and trust me it’s not so easy reaching in and neatly applying really sticky tape, especially for those with large hands. I’ve designed some 3D printed ABS plugs that fit directly into the cutouts of the doors. They snap right in and seal the door completely which should restore the correct mix ratios that the unit thinks it’s achieving. ABS is known to withstand temperatures much higher than what is achieved in the HVAC unit. They definitely make the job much easier and give a nice clean result. If you’re interested, drop me a message and I’ll get you setup.


Thanks for taking the time to write this DIY, I have had the dash off my Jeep before and was about to start on my 02 TT. I will try this first, please send me details on your ABS option.
 

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This write up presents a way to access the blend doors on a MK1 Audi TT without removing the entire dash. The blend doors have foam coverings that are often deteriorated causing bits of foam to blow out of the vents and decreased heat and cooling output due to improper blending of hot and cold air. The blend doors are located behind the radio cage and feed two ducts that go into the two center dash vents. In order to get at them, the glovebox, driver side lower dash, and the entire center section have to come out. The center piece can only be removed last as one mounting location is blocked on each side by the glovebox and lower dash. Removal of these two are somewhat similar. For a quick description you can read the following sections, or skip ahead if you’ve removed these panels before.

*Disclaimer: Some parts of this job can be a bit difficult, especially for those with larger hands, so be sure to read ahead before starting disassembly. The purpose of this write up is to show how I chose to address this issue, anything you do to your car is on you so proceed carefully, don’t do anything you wouldn’t do.

Glovebox:
Note – As you remove screws make sure to support the glovebox as needed so it doesn’t fall or break any of the plastic mounting points under its own weight.
Same with reinstall.

First remove the two screws that are in the top of the lower glovebox tray in the footwell. Pry off the panel that covers the end of the dash on the passenger side. In there, you’ll find a bunch of interior screws. Only some of them need to be removed.

Then open the glovebox and remove the screws located at the top going straight up toward the dash, make sure you’re holding it up because these are the last ones. Lower it slightly and disconnect all the electrical things. There’s a long tab that slides behind the inner dash end panel and a metal panel inside (confusing…pictured below).

Pay attention to this tab, you may have to help guide it out. The glovebox should come straight out or it may require a special touch, either way just be careful of all tabs and don’t force anything. Not a bad time for latch repairs.

Lower Dash:
This is a bit easier than the glovebox. Remove the panel that covers the fuse box. Just like the other side, only some screws in here need to be removed. Also remove the 2 screws underneath in the footwell. The lower dash has two press fit mounts at the top near the cluster, they look like this

Carefully pull the upper edge of the panel forward and they should just pop out. This panel also has the same long tab that slides behind what’s now the fuse panel. You can then free the OBD2 port from the panel, this is some sort of clip in fit, take a good look at it and you should be able to release it by pressing in a couple tabs. Disconnect the headlight switch as well.

Also remove the two small panels on the inside of each footwell, there should be two screws in each, with the front one underneath a little plastic cover.

Radio Cage:
First remove the knee bars.
The ash tray has one screw at the top when you open it. Remove that, and then pull it forward with a slight jiggle to remove.
Using the correct radio keys, pull out and disconnect the radio.

You can then remove the outer plastic trim, which has two screws behind where the radio used to be, and one way underneath behind where the ashtray used to be. Pulling this off will reveal the screws for the HVAC controls. Remove and disconnect them as well.
All that should remain is the plastic cage with the aluminum radio door. There is a screw on each side that goes straight up into the dash, only 1 of 2 are pictured

And there are 2 more underneath the cage.
Make sure all the wires are free when you pull the cage and be sure not to scratch the radio door. Now it should just be you, your heater box, and some wires. You’ll see the two ducts that go into the center dash.

First unclip the wires that are tied down onto the small plastic piece. This piece also has one screw on each side as you can see in the next picture. Remove both screws…you will not be able to remove the whole piece yet, but its pictured for clarity.

You’ll then need to remove this metal piece from the passenger side where the knee bars bolt up in order to make some room for the ducts to move slightly.

Now remove the staples that hold the ducts to the plastic piece. They are on all 4 sides of each outlet (some may have fewer). I straightened out the staple legs and pushed them inside so I could pull the ducts off. You can see one of the staples here.

This one has the legs coming out, some may have the legs going in, those can just be pulled out. This is one of the more difficult parts as the staple on the top side of the top duct (if you have one) is not easy to get to and cannot be seen. You’ll need some kind of pick or long small screwdriver for this. It requires a lot of jostling and squeezing of the ducts, but with some finesse you’ll get them off and be glad to see the infamous blend door…or at least one of them.

After pulling off both ducts, the plastic piece sandwiched between can come out and you’ll see the whole blend door. The ducts have enough play so that the dash vent ends do not need to be disconnected. As pictured above, the door is closed (or open…whatever) but you can plug your HVAC controls back in and play with them until it opens up, granting you access to the second, deeper blend door.

Just scoop out many handfuls from in between the doors and pull off any remaining doodoo foam clinging on to haunt you for another 20 years.

I chose to use HVAC aluminum foil tape to recover my doors, laying horizontal strips over the holes. I tried my best to neatly wrap them around both sides of the door so that there wouldn’t be an exposed sticky side. It’s up to you how particular to be here, but anything is better than the sorry state they’re likely in. Just try to do the cleanest job possible and don’t put tape anywhere it could interfere with the movement of the doors. HVAC tape is really sticky so position the strips carefully and slowly. Once you’re happy…job done. Fiddle with the HVAC controls to test door movement.

Refit the sandwiched plastic piece and press the ducts back into place. You can try to refix them with a staple gun or however you like. They fit pretty snug just slipped back over the lips but refixing is up to you.

Interior reassembly is the reverse. Enjoy better heat and finally an end to the foam blowing out of your vents.


I was also able to design a solution here that is a bit more graceful than covering the doors with HVAC foil tape. That’s how I fixed mine initially and trust me it’s not so easy reaching in and neatly applying really sticky tape, especially for those with large hands. I’ve designed some 3D printed ABS plugs that fit directly into the cutouts of the doors. They snap right in and seal the door completely which should restore the correct mix ratios that the unit thinks it’s achieving. ABS is known to withstand temperatures much higher than what is achieved in the HVAC unit. They definitely make the job much easier and give a nice clean result. If you’re interested, drop me a message and I’ll get you setup.


Thanks for posting this DIY!! I need to do this to our 2001 TT Roadster among other things. I did this several times to my MK II Jetta's back in the day and I always removed the whole dash and I was dreading pulling the dash on the TT.
 
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I am getting ready to repair the blend doors in my wife's 2001 beetle and I am glad for all the advice, but I have one question. What the crap is the holes for to begin with? just looking at them and not being an automotive HVAC engineer but it does not make sense to me.
 

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I am getting ready to repair the blend doors in my wife's 2001 beetle and I am glad for all the advice, but I have one question. What the crap is the holes for to begin with? just looking at them and not being an automotive HVAC engineer but it does not make sense to me.
I am no engineer either, but my speculation is it minimizes the weight of the doors, allowing them to operate easier. Have yet to do this on my coupe yet, but I bought the chrome duct tape for $15 at Lowes.
 

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Discussion Starter · #8 ·
I am no engineer either, but my speculation is it minimizes the weight of the doors, allowing them to operate easier. Have yet to do this on my coupe yet, but I bought the chrome duct tape for $15 at Lowes.
I am an engineer, and I have no clue haha...I'm sure there was a reason for the design, could be to do with managing the airflow pressure or maybe mixing rates...whatever the reason I wish they would've thought ahead on this one, wouldn't have been hard to guess what would happen after a few years of use
 

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The ducts have enough play so that the dash vent ends do not need to be disconnected.
Thank you so much for this and for taking the time to document it. With your instructions I was able to get started on this project over the weekend.

However, either I am doing something wrong, or my 2002 is different from yours, but there is absolutely NO play in those ducts. I think I am going to have to disassemble the dash (next weekend)!
 

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Discussion Starter · #10 ·
Thank you so much for this and for taking the time to document it. With your instructions I was able to get started on this project over the weekend.

However, either I am doing something wrong, or my 2002 is different from yours, but there is absolutely NO play in those ducts. I think I am going to have to disassemble the dash (next weekend)!
Hmmm my guess is that there could be a staple somewhere that you may have missed, I don't remember pulling super hard on them, but might need a decent yank. If you can squeeze the plastic duct easily with your hand there should be some play. If not, check the dash ends of the vent to see if you can get them off up there. I hope you don't have to remove the dash, good luck!
 

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Hmmm my guess is that there could be a staple somewhere that you may have missed, I don't remember pulling super hard on them, but might need a decent yank. If you can squeeze the plastic duct easily with your hand there should be some play. If not, check the dash ends of the vent to see if you can get them off up there. I hope you don't have to remove the dash, good luck!
You are absolutely correct. It is all apart now and I can proceed with the repair! Is there any chance I can get the files from you to print the plugs? Again, I really appreciate this hugely time-saving post.
 

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This write up presents a way to access the blend doors on a MK1 Audi TT without removing the entire dash. The blend doors have foam coverings that are often deteriorated causing bits of foam to blow out of the vents and decreased heat and cooling output due to improper blending of hot and cold air. The blend doors are located behind the radio cage and feed two ducts that go into the two center dash vents. In order to get at them, the glovebox, driver side lower dash, and the entire center section have to come out. The center piece can only be removed last as one mounting location is blocked on each side by the glovebox and lower dash. Removal of these two are somewhat similar. For a quick description you can read the following sections, or skip ahead if you’ve removed these panels before.

*Disclaimer: Some parts of this job can be a bit difficult, especially for those with larger hands, so be sure to read ahead before starting disassembly. The purpose of this write up is to show how I chose to address this issue, anything you do to your car is on you so proceed carefully, don’t do anything you wouldn’t do.

Glovebox:
Note – As you remove screws make sure to support the glovebox as needed so it doesn’t fall or break any of the plastic mounting points under its own weight.
Same with reinstall.

First remove the two screws that are in the top of the lower glovebox tray in the footwell. Pry off the panel that covers the end of the dash on the passenger side. In there, you’ll find a bunch of interior screws. Only some of them need to be removed.

Then open the glovebox and remove the screws located at the top going straight up toward the dash, make sure you’re holding it up because these are the last ones. Lower it slightly and disconnect all the electrical things. There’s a long tab that slides behind the inner dash end panel and a metal panel inside (confusing…pictured below).

Pay attention to this tab, you may have to help guide it out. The glovebox should come straight out or it may require a special touch, either way just be careful of all tabs and don’t force anything. Not a bad time for latch repairs.

Lower Dash:
This is a bit easier than the glovebox. Remove the panel that covers the fuse box. Just like the other side, only some screws in here need to be removed. Also remove the 2 screws underneath in the footwell. The lower dash has two press fit mounts at the top near the cluster, they look like this

Carefully pull the upper edge of the panel forward and they should just pop out. This panel also has the same long tab that slides behind what’s now the fuse panel. You can then free the OBD2 port from the panel, this is some sort of clip in fit, take a good look at it and you should be able to release it by pressing in a couple tabs. Disconnect the headlight switch as well.

Also remove the two small panels on the inside of each footwell, there should be two screws in each, with the front one underneath a little plastic cover.

Radio Cage:
First remove the knee bars.
The ash tray has one screw at the top when you open it. Remove that, and then pull it forward with a slight jiggle to remove.
Using the correct radio keys, pull out and disconnect the radio.

You can then remove the outer plastic trim, which has two screws behind where the radio used to be, and one way underneath behind where the ashtray used to be. Pulling this off will reveal the screws for the HVAC controls. Remove and disconnect them as well.
All that should remain is the plastic cage with the aluminum radio door. There is a screw on each side that goes straight up into the dash, only 1 of 2 are pictured

And there are 2 more underneath the cage.
Make sure all the wires are free when you pull the cage and be sure not to scratch the radio door. Now it should just be you, your heater box, and some wires. You’ll see the two ducts that go into the center dash.

First unclip the wires that are tied down onto the small plastic piece. This piece also has one screw on each side as you can see in the next picture. Remove both screws…you will not be able to remove the whole piece yet, but its pictured for clarity.

You’ll then need to remove this metal piece from the passenger side where the knee bars bolt up in order to make some room for the ducts to move slightly.

Now remove the staples that hold the ducts to the plastic piece. They are on all 4 sides of each outlet (some may have fewer). I straightened out the staple legs and pushed them inside so I could pull the ducts off. You can see one of the staples here.

This one has the legs coming out, some may have the legs going in, those can just be pulled out. This is one of the more difficult parts as the staple on the top side of the top duct (if you have one) is not easy to get to and cannot be seen. You’ll need some kind of pick or long small screwdriver for this. It requires a lot of jostling and squeezing of the ducts, but with some finesse you’ll get them off and be glad to see the infamous blend door…or at least one of them.

After pulling off both ducts, the plastic piece sandwiched between can come out and you’ll see the whole blend door. The ducts have enough play so that the dash vent ends do not need to be disconnected. As pictured above, the door is closed (or open…whatever) but you can plug your HVAC controls back in and play with them until it opens up, granting you access to the second, deeper blend door.

Just scoop out many handfuls from in between the doors and pull off any remaining doodoo foam clinging on to haunt you for another 20 years.

I chose to use HVAC aluminum foil tape to recover my doors, laying horizontal strips over the holes. I tried my best to neatly wrap them around both sides of the door so that there wouldn’t be an exposed sticky side. It’s up to you how particular to be here, but anything is better than the sorry state they’re likely in. Just try to do the cleanest job possible and don’t put tape anywhere it could interfere with the movement of the doors. HVAC tape is really sticky so position the strips carefully and slowly. Once you’re happy…job done. Fiddle with the HVAC controls to test door movement.

Refit the sandwiched plastic piece and press the ducts back into place. You can try to refix them with a staple gun or however you like. They fit pretty snug just slipped back over the lips but refixing is up to you.

Interior reassembly is the reverse. Enjoy better heat and finally an end to the foam blowing out of your vents.


I was also able to design a solution here that is a bit more graceful than covering the doors with HVAC foil tape. That’s how I fixed mine initially and trust me it’s not so easy reaching in and neatly applying really sticky tape, especially for those with large hands. I’ve designed some 3D printed ABS plugs that fit directly into the cutouts of the doors. They snap right in and seal the door completely which should restore the correct mix ratios that the unit thinks it’s achieving. ABS is known to withstand temperatures much higher than what is achieved in the HVAC unit. They definitely make the job much easier and give a nice clean result. If you’re interested, drop me a message and I’ll get you setup.


 

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Matriss - Thank you for providing such detail and photos.
I am planning on effecting your repair before the snow flies/
Are the plugs you mentioned available for purchase, or can you provide the file?
I expect to pay for its use.
 

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This write up presents a way to access the blend doors on a MK1 Audi TT without removing the entire dash. The blend doors have foam coverings that are often deteriorated causing bits of foam to blow out of the vents and decreased heat and cooling output due to improper blending of hot and cold air. The blend doors are located behind the radio cage and feed two ducts that go into the two center dash vents. In order to get at them, the glovebox, driver side lower dash, and the entire center section have to come out. The center piece can only be removed last as one mounting location is blocked on each side by the glovebox and lower dash. Removal of these two are somewhat similar. For a quick description you can read the following sections, or skip ahead if you’ve removed these panels before.

*Disclaimer: Some parts of this job can be a bit difficult, especially for those with larger hands, so be sure to read ahead before starting disassembly. The purpose of this write up is to show how I chose to address this issue, anything you do to your car is on you so proceed carefully, don’t do anything you wouldn’t do.

Glovebox:
Note – As you remove screws make sure to support the glovebox as needed so it doesn’t fall or break any of the plastic mounting points under its own weight.
Same with reinstall.

First remove the two screws that are in the top of the lower glovebox tray in the footwell. Pry off the panel that covers the end of the dash on the passenger side. In there, you’ll find a bunch of interior screws. Only some of them need to be removed.

Then open the glovebox and remove the screws located at the top going straight up toward the dash, make sure you’re holding it up because these are the last ones. Lower it slightly and disconnect all the electrical things. There’s a long tab that slides behind the inner dash end panel and a metal panel inside (confusing…pictured below).

Pay attention to this tab, you may have to help guide it out. The glovebox should come straight out or it may require a special touch, either way just be careful of all tabs and don’t force anything. Not a bad time for latch repairs.

Lower Dash:
This is a bit easier than the glovebox. Remove the panel that covers the fuse box. Just like the other side, only some screws in here need to be removed. Also remove the 2 screws underneath in the footwell. The lower dash has two press fit mounts at the top near the cluster, they look like this

Carefully pull the upper edge of the panel forward and they should just pop out. This panel also has the same long tab that slides behind what’s now the fuse panel. You can then free the OBD2 port from the panel, this is some sort of clip in fit, take a good look at it and you should be able to release it by pressing in a couple tabs. Disconnect the headlight switch as well.

Also remove the two small panels on the inside of each footwell, there should be two screws in each, with the front one underneath a little plastic cover.

Radio Cage:
First remove the knee bars.
The ash tray has one screw at the top when you open it. Remove that, and then pull it forward with a slight jiggle to remove.
Using the correct radio keys, pull out and disconnect the radio.

You can then remove the outer plastic trim, which has two screws behind where the radio used to be, and one way underneath behind where the ashtray used to be. Pulling this off will reveal the screws for the HVAC controls. Remove and disconnect them as well.
All that should remain is the plastic cage with the aluminum radio door. There is a screw on each side that goes straight up into the dash, only 1 of 2 are pictured

And there are 2 more underneath the cage.
Make sure all the wires are free when you pull the cage and be sure not to scratch the radio door. Now it should just be you, your heater box, and some wires. You’ll see the two ducts that go into the center dash.

First unclip the wires that are tied down onto the small plastic piece. This piece also has one screw on each side as you can see in the next picture. Remove both screws…you will not be able to remove the whole piece yet, but its pictured for clarity.

You’ll then need to remove this metal piece from the passenger side where the knee bars bolt up in order to make some room for the ducts to move slightly.

Now remove the staples that hold the ducts to the plastic piece. They are on all 4 sides of each outlet (some may have fewer). I straightened out the staple legs and pushed them inside so I could pull the ducts off. You can see one of the staples here.

This one has the legs coming out, some may have the legs going in, those can just be pulled out. This is one of the more difficult parts as the staple on the top side of the top duct (if you have one) is not easy to get to and cannot be seen. You’ll need some kind of pick or long small screwdriver for this. It requires a lot of jostling and squeezing of the ducts, but with some finesse you’ll get them off and be glad to see the infamous blend door…or at least one of them.

After pulling off both ducts, the plastic piece sandwiched between can come out and you’ll see the whole blend door. The ducts have enough play so that the dash vent ends do not need to be disconnected. As pictured above, the door is closed (or open…whatever) but you can plug your HVAC controls back in and play with them until it opens up, granting you access to the second, deeper blend door.

Just scoop out many handfuls from in between the doors and pull off any remaining doodoo foam clinging on to haunt you for another 20 years.

I chose to use HVAC aluminum foil tape to recover my doors, laying horizontal strips over the holes. I tried my best to neatly wrap them around both sides of the door so that there wouldn’t be an exposed sticky side. It’s up to you how particular to be here, but anything is better than the sorry state they’re likely in. Just try to do the cleanest job possible and don’t put tape anywhere it could interfere with the movement of the doors. HVAC tape is really sticky so position the strips carefully and slowly. Once you’re happy…job done. Fiddle with the HVAC controls to test door movement.

Refit the sandwiched plastic piece and press the ducts back into place. You can try to refix them with a staple gun or however you like. They fit pretty snug just slipped back over the lips but refixing is up to you.

Interior reassembly is the reverse. Enjoy better heat and finally an end to the foam blowing out of your vents.


I was also able to design a solution here that is a bit more graceful than covering the doors with HVAC foil tape. That’s how I fixed mine initially and trust me it’s not so easy reaching in and neatly applying really sticky tape, especially for those with large hands. I’ve designed some 3D printed ABS plugs that fit directly into the cutouts of the doors. They snap right in and seal the door completely which should restore the correct mix ratios that the unit thinks it’s achieving. ABS is known to withstand temperatures much higher than what is achieved in the HVAC unit. They definitely make the job much easier and give a nice clean result. If you’re interested, drop me a message and I’ll get you setup.


Any chance I could get the stp files for those plugs?
 

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Just wanted to thank you for this. I will be trying this on my Mk1 TT this week.

For others who aren't sure whether the loss of heat (in my case) or loss of cooling is from the blend door foam problem, just go out and buy a cheap inspection camera that works off your phone. It cost me $9, and I fished it up the driver side floor duct to take a look and verify that there is no foam left at all. Saved me replacing the thermostat, cooling sensor, flushes, etc. in the troubleshooting process, like others have reported doing.

Can't wait to have heat again.
 

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Just wanted to thank you for this. I will be trying this on my Mk1 TT this week.

For others who aren't sure whether the loss of heat (in my case) or loss of cooling is from the blend door foam problem, just go out and buy a cheap inspection camera that works off your phone. It cost me $9, and I fished it up the driver side floor duct to take a look and verify that there is no foam left at all. Saved me replacing the thermostat, cooling sensor, flushes, etc. in the troubleshooting process, like others have reported doing.

Can't wait to have heat again.
Just finished the tape job. Took about 3 hours, and then there was heat!

Thanks again for this great fix!

On a side note, I saw that some people said the foil tape fix failed. Any idea how long the foil tape fix lasts, in general?
 

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On a side note, I saw that some people said the foil tape fix failed. Any idea how long the foil tape fix lasts, in general?
So that's going to depend on which foil tape you bought. Most people will spring for the cheaper $7-8 rolls, but those are typically only rated for 40°F to 200°F... both of which can easily be exceeded on a regular basis.

I know Nashua makes an "Extreme Weather" version that is rated for -35°F to 260°F - that's $22 for a 50 ft roll; as well as a "Premium Foil" version that is rated for -25°F to 325°F and costs about $17 for a 60 ft roll.
 
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So that's going to depend on which foil tape you bought. Most people will spring for the cheaper $7-8 rolls, but those are typically only rated for 40°F to 200°F... both of which can easily be exceeded on a regular basis.

I know Nashua makes an "Extreme Weather" version that is rated for -35°F to 260°F - that's $22 for a 50 ft roll; as well as a "Premium Foil" version that is rated for -25°F to 325°F and costs about $17 for a 60 ft roll.
I used the cheaper stuff. Looks like I'll have to redo it at some point in the future. Thanks for the information.
 
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