DIY: How to fix air blend door MK4 TDI no cabin heat problem

Rickstah

Veteran Member
Joined
Feb 5, 2002
Location
Yukon, Oklahoma
TDI
NB, 2002, green, Eurotek STG1
OK, I finished the job, wow pretty tedious and not easy to hold those little plugs when you have them greased up with rtv. I had some earlier comments but decided to just do a start to finish with some pics, hopefully I learned a couple of things that will help you. I think I would have gone with the tape if I had known how tedious it was to use rtv and the plugs. Also, keep super glue handy. When you remove the center console (see youtube instructions in an earlier post from me) you may find some edges that hold the t20 screws to be cracked or missing.

I got the opening cut out. I was able to put small led light down in the channel and it worked ok.




The front door was devoid of foam, the back door had foam on all the holes but the top left one, can't see in the pic, however it is deceiving, the foam over the holes is vapor-thin so will need to clean them all off. I was a bit concerned about the amount of force needed to clip the plugs into the holes, didn't want to knock that door off those itty bitty flanges holding it in place, plus it is further back than I expected almost an arms length. I can see why adhesive tape of some kind has its uses in this repair.

The front door went first. The rectangular plugs, at least, will insert with minimal difficulty, a bit more difficult to remove if you do it before adding the rtv. Using the black Right stuff sealant with 90 minute cure time. I did discover that the selector switch for it (dash/floor-dash/defrost) moves an unseen door up under the dash somewhere to send it all to the windshield when you select defrost. Now I wonder if it has foam on it, too, hmmm.

The red arrow points to the left side of the rear door (heat blend). I didn't see it at first but then discovered there are seven round holes in that narrow area. Also, keep that thing up against the little channel as much as possible because there is a stable wormhole underneath that door and it leads to the Delta quadrant.



I dropped one small round and one mid-size round plug. they bounced into that opening and never made a sound, they could still be falling. Anyway, you will have to risk dialing it back some when you go to plug the bottom hole and it is awkward because about a quarter of the hole is below the level of the channel. Since I was missing one round plug I had to use the high-temp aluminum tape. The adhesive on that stuff is crazy sticky and a bit difficult to maneuver but if you use small strips it is still difficult but after three or four tries you will still need two or three more tries until you get a couple on there that still leave a small gap at which point you mumble screw it and call it good. Maybe that won't happen to you. The place isn't exactly hermetically sealed anyway, you will see when you move the doors back and forth. If you go with the plugs on ebay you may want to negotiate an extra midsized round plug and maybe two extra small round plugs, they can disappear in a blink.

About the mid-sized round plug that also turned into dark matter and went on the rear door, I also used some tape for one of those holes, if you cut a couple of squares 1.5x1.5 inches you will then need to cut a smaller strip to compensate for your lack of eyesight since I had already used the other round plugs and it was one of the ones on the right side. If you are smart you will overnight some kevlar arm sleeves to wear when you do this job, at least a long-sleeved shirt. My forearms look like I played slapjack with Edward Scissorhands. I advise trying to fill the heat blend door holes from the right first, that way if you lose one you got the most difficult ones done first and the tape is easier to apply to the others.



Make sure you have one of those spring grabbies in case the plug squirts out of your fingers and goes through the opening behind the door :sneaky:. It worked out the first time. There are also more than one size rectangular openings on mine. Don't do what I did and choose the smaller size and try to put it in the larger one, I think the bottom hole. I was able to fish it out of there after about 16 hours.

This has not been an easy gig. By the time I got the rtv around the inside edge of the plug it becomes kind of slippery and not easy to center by feel, and the small ones are worst. My arms aren't humongus but it is not easy to bend the wrist while keeping a grip on the edge of the plug...the tiny minuscule spots where the rtv didn't get, lol, and get it centered. I managed to get one pushed into the hole by using some gorilla tape bits on the outside for a better grip but it doesn't last, sweaty hands, gloves stick to the rtv, etc. So, I punted. I took super glue and glued the head of a zip tie to the outside of the plug and once it dried (if you use Gorilla super glue let it sit for an hour at least or it will come loose and you will find the wormhole) I was able to hold them from that and maneuver the plugs to the hole without smearing the rtv on gripping fingers so it went better after that. I mean the ones you can't see you will still get close but not there and smear it back and forth but finally feel it go into the opening and then you hope there was enough rtv to still seal, lol. It looks stupid but they went on. Sometime about then I realized there were seven more holes right behind that middle vertical piece, that pivoted with the big rear door, sigh. It was soulcrushing but I battled back with some chips and salsa and walking away until the next day, no need to be one of the working wounded at 1 am, you could find yourself asleep inside the 90 degree car.

After I got it all done the tape once again made its value known, I was able to mount the original piece kind of in the middle of the carved out area (had to take a bit more off to give my arms more room) and then built up the edges and it was pretty tight.


I am writing this so you will have full disclosure if you are on meds and are thinking of trying this method, lol. If you can just reach in and put these plugs in with the rtv sealant on them without any issue you are either double jointed or have girl arms/hands :), J/K. On balance using the tape may have been easier overall with not having to deal with the rtv. I did use the spring grabbie to put in the top two holes on the heat blend door at back. I grabbed the zip tie bit and was able to bend the spring back up after it got past the opening and I was scrunched down and it just maneuvered right into the holes. I let it sit like that for a few minutes because one of the grabbie pieces was kind of wedged behind the zip tie but after it firmed up a bit I was able to expand the arms and it came loose. Good luck! My A/C is ICE COLD NOW even when ambient is in high 90s.









 

Rickstah

Veteran Member
Joined
Feb 5, 2002
Location
Yukon, Oklahoma
TDI
NB, 2002, green, Eurotek STG1
Thanks for the awesome right up. Question did you actually need to put RTV on them? Would they not stay in otherwise?
No, they were very loose, jiggled if you touched them or reached behind to push back out. I was hoping for a more rubbery plug when I ordered that would kind of go in like a rubber bushing.

I should say it was loose for my A4, probably the same for other A4s, not sure about the pattern or size on different vehicles.

I am still bugged about the invisible door that opens when you switch to full defrost, guess I need to figure out how to get to it, thinking the big plugs may go to it. Anyone found that one yet?
 
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KrashDH

Top Post Dawg
Joined
Dec 22, 2013
Location
Washington
TDI
2002 Golf
No, they were very loose, jiggled if you touched them or reached behind to push back out. I was hoping for a more rubbery plug when I ordered that would kind of go in like a rubber bushing.

I should say it was loose for my A4, probably the same for other A4s, not sure about the pattern or size on different vehicles.

I am still bugged about the invisible door that opens when you switch to full defrost, guess I need to figure out how to get to it, thinking the big plugs may go to it. Anyone found that one yet?
Yeah, those plugs almost look 3D printed. Not sure why you couldn't injection mold some rubber plugs that fit the profile of the holes. That work eliminate the need for RTV and make the process a bit easier.

What car did you do this on @Rickstah (golf/Jetta or NB)?
 

Rickstah

Veteran Member
Joined
Feb 5, 2002
Location
Yukon, Oklahoma
TDI
NB, 2002, green, Eurotek STG1
Yeah, those plugs almost look 3D printed. Not sure why you couldn't injection mold some rubber plugs that fit the profile of the holes. That work eliminate the need for RTV and make the process a bit easier.

What car did you do this on @Rickstah (golf/Jetta or NB)?
Sorry, just got back here after being too busy. My 2002 A4 NB. I can see where it may be cheaper to create the little plugs that feel like checkers and the volume may not be large, I guess. Actually, after it was all over except for those holes on the narrow side of the temp door I realized the hvac adhesive tape would likely have been much easier than the rtv. Cut some small squares and just keep adding them until all the holes were covered...although a couple were really out of sight and taking your gloves off and feeling around while you maneuvered the plugs around so they would kind of slide into the holes was more intuitive than tape would have been. All I know is I didn't have to remove the dash, lol...I shouldn't act happy, the universe may zap my heater core, lol.
 

PakProtector

Veteran Member
Joined
Jan 5, 2014
Location
AnnArbor, MI
TDI
Mk.4's and the Cummins
Mentioned this in the 'what I did to my mk4 today' thread; on the right side, far door, put in the big plugs first. They can't go in the small holes. Use a mirror and be sure you have them all plugged. Then do the little round plugs. It will be a PITA if you drop a small plug through a big hole.

I also wound up with 3 of the biggest round plugs as 'extry'...I am sure that no such holes exist in the two accessible doors on the three Jetta's I have done( '00, '02 and '04 ). Even wid the silicone adhesive mess, this was a lot nicer to do than the tape method I did on the first two.

They are indeed 3D printed. Even with proper injection molding and the addition of some snaps I would still glue them in. The thought of them rattling just troubles me. Let alone the risk to breaking something whilst snapping them in.
cheers,
Douglas
 

Another

Member
Joined
Apr 22, 2019
Location
Montreal South-Shore
TDI
MK4 golf BEW + wagon ALH
I'll gonna cry.....why MK4 have same problemes at this point as old MK2's ? :(
Did same work back in time on my both mk2... i can't imagine that same thing will be needed here knowing that that the heater core case is much harder to disassembling
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
I'll gonna cry.....why MK4 have same problemes at this point as old MK2's ? :(
Did same work back in time on my both mk2... i can't imagine that same thing will be needed here knowing that that the heater core case is much harder to disassembling
VW never intended for you to keep the car this long. Although I gotta say, it is a strange choice of materials for an HVAC door.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Suggestions/Thoughts ..

I purchased the plug kit and hope to tackle this job on my Jetta after the holidays. I've done it with the heat tape on several New Beetles. So, this will be a first for me on a Jetta.

So, looking and reading what Rickstah posted has given me an idea. I plan to install a rather large head screw in the center of the plastic pieces. The screw will remain in the plug. Using a magnet wand, It would seem easy enough to put the plugs in place with the RTV on them. A long screw driver could be used to hold the plug in place while pulling the magnet loose.

Thoughts?
 

Cosmo's UNA

Active member
Joined
Nov 20, 2019
Location
VIRGINIA
TDI
2003 Jetta TDI Wagon
Heavy duty aluminum HVAC tape is the way to go. Your blend doors will be as good or better than what rolled off the factory. I have to agree, Why the holes and foam in the first place? I have super heat (also did a recent plastic cardboard radiator block piece) and cold AC.
 

jokila

Vendor
Joined
Dec 3, 2004
Location
Houston, Texas
TDI
2003 Jetta GLS, Manual
Heavy duty aluminum HVAC tape is the way to go. Your blend doors will be as good or better than what rolled off the factory. I have to agree, Why the holes and foam in the first place? I have super heat (also did a recent plastic cardboard radiator block piece) and cold AC.
Definitely don't use that thin stuff easily available at the hardware stores. The stuff should be thicker than the most heavy duty aluminum foil.

I went beyond that to help make the sealing better and glued on a thin silicone on top of the tape. Not sure if it was worth it but it seems more "solid" when you change door positions than without. Either way, just doing the work is going to get you fixed up.
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
I recently used 1/8"high temp magnetic sheet ( like a refrigerator magnet) from McMaster Carr to cover the doors. It is pretty easy to scoot it into place, the "glue" never gives out, and I firm up its location with a couple of drops of crazy glue. So far so good.
 
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PakProtector

Veteran Member
Joined
Jan 5, 2014
Location
AnnArbor, MI
TDI
Mk.4's and the Cummins
I recently used 1/8"high temp magnetic sheet ( like a refrigerator magnet) from McMaster Carr to cover the doors. It is pretty easy to scoot it into place, the "glue" never gives out, and I firm up its location with a couple of drops of crazy glue. So far so good.
Whaaaaaat? What is magnetic there? I must have missed something, cause after a look I assumed the doors were AL...

Now if you found the mythical AL magnet... :D
cheers,
Douglas
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
One has to really wonder why the doors, holes and foam.
My guess is solid steel doors would be kind of clunky and so the reduced the mass with the holes then adding foam to soften the closing of them when hitting the surfaces. Also, the foam letting a small amount through to reduces the effort to open a door against the air pressure of a blower fan on "HI". Could be to enhance the knob feel of the process.
It all (or most of it) works very well until the foam falls apart...like it is supposed to after a dozen years or so. Anyone know if they are still using this design in the later cars? Hey, why not? The cost of having this repaired by a dealership or even an independent shop just may be the tipping point for many owners saying good bye to an older vehicle and buying a brand spanking new VW! Why should VW care about anything that is out of their warranty responsibility?
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Actual DUCT TAPE -- the fire-rated stuff you're supposed to use for ductwork (it has a UL rating on it if you're in the US) ain't going anywhere once it is stuck on whatever you stick it on. Same stuff you use (or should be using!) for your dryer exhaust duct. It's metal, the adhesive is strong and its pretty tough stuff.
 

bhef

Well-known member
Joined
Oct 13, 2021
Location
Southern California Rural
TDI
2000 Jetta 1.9 TDI - 5 Speed
I'm really hoping somebody can help me out here...

Did this fix and now I only have air from the center dash vents. Even on max (4), the side dash vents have barely (next to no) airflow from them.

Anyone have any ideas??

EDIT: Figured it out... when reinstalling the box make sure the divider from the upper part it goes into is in the correct position: the middle. Originally put it back and it got stuck behind the box cutting off air to the outer dash vents
 
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Wild Bill

New member
Joined
Aug 8, 2022
Location
Staten Island
TDI
Mk4
I’ll be attempting this blend door fox after the summer. I plan on using the shortcut method. I just wish someone made a start to finish video on doin the complete job disassembling everything. Unless I couldn’t find a good video. Such a common problem I wish there was a full write up. Thx guys
 

Nuje

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Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2015 Sportwagen; Golf GLS 2002 (swap from 2L gas); 2016 A3 e-tron
HumbleMechanic has a pretty good video (btw, I don't know if there's anyone who does better-produced videos- not just how-to, but lighting, audio, editing, etc. - than this guy; simply top-notch videos) on the "quick" method - pulling the centre console to get to the door behind the stereo.
This is my plan should the time come that I need to do this.

 
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Rickstah

Veteran Member
Joined
Feb 5, 2002
Location
Yukon, Oklahoma
TDI
NB, 2002, green, Eurotek STG1
My fix is still working, apparently, but I have seen some recent chunks working their way out and I am thinking there is another blend door of some type at the top under the dash somewhere that is disintegrating but have not seen this addressed if true. Has anyone had to resolve this issue?
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2015 Sportwagen; Golf GLS 2002 (swap from 2L gas); 2016 A3 e-tron
I recently pulled the HVAC box (first timer) and had some issues - asked a couple questions in a separate thread, but figured it'd be worthwhile posting my experience / revelations in this stickied thread for visibility.

Issue #1: The front-most facing door wasn't closing all the way; this is as far as it would close:


Turns out that, while I *thought* I'd kept the cable in place, the cable housing (white, yellow, or green - this was the yellow one) that's clamped down by a spring clip, had slipped somewhat. Following the instructions (below), I nudged the yellow housing about 1cm further back, which enabled the cable travel to push the door all the way closed (note that page in the manual for how-to adjustments of the other cables - they're in adjacent pages).


Issue #2: I couldn't get whole HVAC box separated top from bottom: I thought I had all of the screws removed, but when I'd finished putting in the plugs and aluminum-taping over some other parts via the air outlet ports, (not to mention fighting to get the evaporator back in) and I was vacuuming up all the nooks and crannies, something caught my eye in this cranny:


Behold, ye "missing" screw:
 
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JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
I recently pulled the HVAC box (first timer) and had some issues - asked a couple questions in a separate thread, but figured it'd be worthwhile posting my experience / revelations in this stickied thread for visibility.

Issue #1: The front-most facing door wasn't closing all the way; this is as far as it would close:


Turns out that, while I *thought* I'd kept the cable in place, the cable housing (white, yellow, or green - this was the yellow one) that's clamped down by a spring clip, had slipped somewhat. Following the instructions (below), I nudged the yellow housing about 1cm further back, which enabled the cable travel to push the door all the way closed (note that page in the manual for how-to adjustments of the other cables - they're in adjacent pages).


Issue #2: I couldn't get whole HVAC box separated top from bottom: I thought I had all of the screws removed, but when I'd finished putting in the plugs and aluminum-taping over some other parts via the air outlet ports, (not to mention fighting to get the evaporator back in) and I was vacuuming up all the nooks and crannies, something caught my eye in this cranny:


Behold, ye "missing" screw:
Don’t know if this was mentioned in the thread earlier…
Perfect time to replace the heater core whether it’s leaking now or not. It’s not that expensive and it seems like it will start to leak sooner or later.
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2015 Sportwagen; Golf GLS 2002 (swap from 2L gas); 2016 A3 e-tron
I'd actually thought of that and had one on order. But then when I did pull it out.... man - that thing looked brand spankin' new! Never had heat problem and it looks perfect, so I put it back in.
 
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