Cabin heat out of control

The rotary heat control knob is set to blue (counter clockwise all the way) and the blower is set to zero (off.) Yesterday the outside air temperature was 89°F and inside it was 118° w/ all the windows open.
There must be a valve that's stuck in the open position that permits engine coolant to constantly enter the cabin. Question is, how do I remedy this problem?

Most likely it's the air blend door.

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phaser said:

Most likely it's the air blend door.
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OK. So there's a broken linkage which connects the rotary temp control knob w/ the air blend door?
Can anyone elaborate? I'm reasonably handy w/ a wrench. What's involved in the repair?

I have a feeling you aren't going to like the answer. I'm pretty sure it involves removing your entire dash, but I'll let others chime in.

Might be the cable or a worn temperature blend door support pin that has dropped down and disengaged from the blend door.

Here's a video showing the support pin, and where the cable was the fix.

https://www.youtube.com/watch?v=7mR6mH3ZlOI

Go to 1:52 and stop the video for a good look.

The white cable connects to the arm and to the support pin. It's just to the left of the white cable.

That pin has partially dropped down even though the author of the video doesn't realize it. There should be no gap. I know because I replaced mine sometime back.

Here's what the support pin looks like: https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/blend-door-support-pin/1h0819136/

Unfortunately the support pin (VW part # 1H0819136) is no longer available, not even through 1st VW Parts. Maybe a member here knows where to get one.

Replacing the pin, should you find one, doesn't require removing the dash.

Hopefully it's just a cable issue for you.

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belome said:

I have a feeling you aren't going to like the answer. I'm pretty sure it involves removing your entire dash, but I'll let others chime in.

Click to expand...

Hopefully not. The issue you're thinking off is poor heating system performance due to the foam deteriorating on the blend door. Too much heat is likely a symptom of a bad/disconnected/stuck linkage.

I would suspect the temp cable or something related to it.

The "heat" is always "on", in that the coolant is always flowing through the heater core in the dash. The only thing that regulates temp is the door which is worked via a cable from the temp knob.

You can access the cables without too much drama at least to see that they are moving on the ends away from the control head by removal of the lower trim bits and the forward trim panel near the accelerator pedal.

phaser said:

Might be the cable or a worn temperature blend door support pin that has dropped down and disengaged from the blend door.
Here's a video showing the support pin, and where the cable was the fix.
https://www.youtube.com/watch?v=7mR6mH3ZlOI
Go to 1:52 and stop the video for a good look.
The white cable connects to the arm and to the support pin. It's just to the left of the white cable.
That pin has partially dropped down even though the author of the video doesn't realize it. There should be no gap. I know because I replaced mine sometime back.
Here's what the support pin looks like: https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/blend-door-support-pin/1h0819136/
Unfortunately the support pin (VW part # 1H08191360) is no longer available, not even through 1st VW Parts. Maybe a member here knows where to get one.
Replacing the pin, should you find one, doesn't require removing the dash.
Hopefully it's just a cable issue for you.
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Click to expand...

That video is great, just what I was hoping for. Now I have a place to start.
THANK YOU phaser!

oilhammer said:

I would suspect the temp cable or something related to it.
The "heat" is always "on", in that the coolant is always flowing through the heater core in the dash. The only thing that regulates temp is the door which is worked via a cable from the temp knob.
You can access the cables without too much drama at least to see that they are moving on the ends away from the control head by removal of the lower trim bits and the forward trim panel near the accelerator pedal.

Click to expand...

I'll be able to investigate the fix over the w/e. Thanks oilhammer!

More to read, with links.

http://forums.tdiclub.com/showthread.php?t=292850

Some other videos:

https://www.google.com/search?q=tdi+temperature+blend+door+support+pin&source=lnms&tbm=vid&sa=X&ved=0ahUKEwi2lITlusjWAhUR12MKHVJICqwQ_AUIDCgD&biw=1090&bih=646

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I made the time to attempt the fix after watching the videos. What surprised me was just how little access there is. One person mentioned removing the drivers seat, but IMO that wouldn't help. One has to get behind the go and brake pedals, and there's just no room available.
I used a camera to get a sight picture and saw that the bushing indeed had dropped down out of where it belongs. I then managed to get a finger under the bushing and push up. Then I moved the temperature control knob through its excursion to verify the mechanism was moving as it should. I did nothing other than that and assumed that friction was holding the bushing in place. Did I get lucky? Will the bushing eventually fall down & out again?
I toyed w/ the idea of putting a bonding agent (something like Shoe Goo) around the bushing to make the connection permanent, but I didn't. I also thought about using .032 stainless steel lockwire externally around the mechanism to hold it up in place. Then I laughed at the effort required to do that w/ such restricted access.
I then put all the trim pieces back and decided to pretend I fixed it. It was nice being able to control the temp again and I appreciate the helpful posts that were made in response to my request for help.
Knowledge is power, this forum rocks!

Art van Law said:

What surprised me was just how little access there is.

Click to expand...

My big hands needed access from both driver and passenger sides, and it wasn't easy removing the cable and support pin so I could disassemble and connect the new pin to the control arm, and then get it back together. It was very difficult, but doable.

Art van Law said:

Will the bushing eventually fall down & out again?

Click to expand...

Absolutely. Once the littler nubbins that lock it into place have worn down, there's nothing to keep the pin in place. It will fall down again.

Art van Law said:

I toyed w/ the idea of putting a bonding agent (something like Shoe Goo) around the bushing to make the connection permanent,...

Click to expand...

NO! No bonding agents, or glue etc. That support pin has to rotate in order to move the air blend door. This is why the little nubbins that lock it into place eventually wear out.

I would suggest a short little post with a small point of some sort between the base of the pin and the floor/hump (I'm thinking something like a short blunt pencil for example), just long enough to apply some pressure to keep the pin from sliding down. The small end with the point would fit into the phillips screw head slot that attaches the arm to the pin.

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phaser said:

NO! No bonding agents, or glue etc. That support pin has to rotate in order to move the air blend door. This is why the little nubbins that lock it into place eventually wear out.
I would suggest a short little post with a small point of some sort between the base of the pin and the floor/hump (I'm thinking something like a short blunt pencil for example), just long enough to apply some pressure to keep the pin from sliding down. The small end with the point would fit into the phillips screw head slot that attaches the arm to the pin.
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Click to expand...

I read that the support pin has to rotate in order to move the air blend door, but amyloid plaques are preventing me from understanding just what's going on internally. You then suggest an external support underneath the bushing to prevent it from falling down. That I can visualize.
But one more thought: would applying a small piece of silver tape to the bushing b4 pushing it up and back inside the housing work? I'm thinking it would create friction thereby preventing it from falling down. (or would that small piece of tape prevent rotation of the support pin just as glue would?)

Go ahead and try the tape, but it may be difficult to get back in due to slightly expanding the pin diameter.

Keep in mind that when inserting the pin, you need to be able to rotate it so the pin slot lines up with the blend door shaft and engages correctly. That has to be done by feel. It's not easy given the limited space.

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phaser said:

Go ahead and try the tape, but it may be difficult to get back in due to slightly expanding the pin diameter.
Keep in mind that when inserting the pin, you need to be able to rotate it so the pin slot lines up with the blend door shaft and engages correctly. That has to be done by feel. It's not easy given the limited space.
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Click to expand...

I must have gotten lucky b/c when I forced the pin up into the housing...that's all I did. I was unaware of the need to line up the pin slot w/ the blend door. As I said, all I did was force it up and in.
I hope NEVER to have to go the route of trying the tape trick. (B/c I'm unlikely to be as lucky as I was on my initial try.)
Thanks for the support along the way. I am sure happy not to be baking.
I see your mileage is way up there. I'm pushing 327K myself. Rust has gotten the best of my fenders and lower door jams. Not sure how much longer money infusions will keep mine going. The inspection is due Jan 2019 so that's a goal for now. The fuel pump and the turbo are original!

Here's some more how-to reading for you:

http://forums.vwvortex.com/showthre...nd-door-issue)/page2&highlight=air+blend+door

Your current toughest problem is probably finding a new pin. There's thousands of them in wrecking/recycling yards, but you take your chances with those since they're likely to be the same age.

Thanks for the Vortex link Norman. I agree that using the pin from a parts car is not ideal. As someone mentioned, a 3-D printer would be the way to go. Undoubtedly, more of these pins will start to fail, hence the need exists for this part.
I wonder which model years are affected. Is it only the ALH model (2000 - 2003) or others that utilize this particular pin 1H0819136 to operate the blend door?

Art van Law said:

I wonder which model years are affected. Is it only the ALH model (2000 - 2003) or others that utilize this particular pin 1H0819136 to operate the blend door?

Click to expand...

That pin was used in the A4 platform 2000-2004 according to this eBay listing:

http://www.ebay.com/itm/2000-2004-V...pport-Pin-GENUINE-OEM-1H0819136-/191863083628

That's a lot of potential pin sales.

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I have a few new ones available.

kleinergti1 said:

I have a few new ones available.

Click to expand...

Is thatyour eBay ad for blend door support pins at $42 each?


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Art van Law said:

............... As someone mentioned, a 3-D printer would be the way to go. .........................

Click to expand...

I do CAD, can't imagine hours you'd need to model that piece for the printer.
If we're gonna make a couple thousand, then you could do it.

I have a NIB full HVAC box with evaporator that I'd love to unload. $100 shipped. Email me. Robby at runonbeer dot com