SL-Class (R129) 1990-2002: SL 280, SL 300, SL 320, SL 500, SL 600, SL 60 AMG

SL/R129: Dash center and side vent rollers

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Old 07-26-2022, 01:40 PM
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Dash center and side vent rollers

Howdy.
Wondering what you guys think about this.
For two years the passenger side vent never had flow in open or closed position.
Now the center vent started going in and out. The vacuum connection is fine behind the engine and playing with the center roller it would blow well in open, but now in closed position too.
As I started to take out the center vent, the passenger vent came to life first time in 2 years. So i know its the rollers.

I took it apart and all


I see is some corrosion on the board.

Any ideas what to do here? I suppose a used one from ebay would work, but who knows what the condition of that will be. Id hate to prop open the center vent open manually as everything else works great.
Old 07-26-2022, 02:41 PM
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I bought another center vent years ago so I could use parts from both to make one.

By all means, take the vent apart and make sure to (gently) remove any corrosion on the boards and ensure that the electrical connection from the thumb wheels to the big pin connector in the back make positive connections.

Completely taking apart the center vent is something of a challenge as every slat and vertical piece comes loose. And the vents will need to be engaged into their respective sliders again. It's a fun puzzle, but patience and care will prevail into a working center vent.

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Old 07-26-2022, 03:07 PM
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Thanks. Well I put it back in the car after cleaning it and I am puzzled.

Half the the time the center vent works when it wants to, Wheel in closed or open or mid way position. Passenger side vent started coming on and off at times now first time in years.

Question. when closing the center vent, will it cancel out the Red/Blue button and turn them off? Mine doesnt do it.

The fact that it has a mind of its own makes me think its not a vacuum issue.

http://manual.startekinfo.com/manual/JSP/cc/3_8/m12.jsp. Gonna run these tests.
Thanks

Last edited by tbilisi79; 07-26-2022 at 03:22 PM.
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Old 07-26-2022, 05:10 PM
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Well I just ran codes it looks like all 3 rollers work. The voltage was at 4.0 open and 0.6 closed on all 3.
No Codes stored.


Weirdest thing is if I play with the roller open and closed, the center vent starts blowing in half way position.
Still don’t get why the center was blowing cold with the roller in closed position the other day.

Started the car now, the center will blow cold with the vent open or in closed position, make no difference. Can not pin point the trigger, but it blow when it wants to.

Last edited by tbilisi79; 07-26-2022 at 07:32 PM.
Old 07-26-2022, 10:18 PM
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Sounds like you might have to move on the the vacuum pods and their respective vacuum lines to the HVAC controller.

The HVAC controller gets its vacuum from the firewall distribution block and the block gets 3 vacuum sources. The engine, the vacuum reservoir in the passenger wheel well and the vacuum pump in the trunk.

When I replaced my evaporator, I took the opportunity to replace or repair all 11 HVAC vacuum pods and inspect the whole vacuum system. There is a single clear vacuum line running the length of the car from the distribution block to the pump in the trunk. That line was brittle and broken in at least five places. I replaced the line and it fixed a lingering center vent issue when the car accelerated hard.

I documented the evaporator swap on either this site or BW. Check it out for some insight.
Old 07-27-2022, 03:15 AM
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Did you cheked the distributor? If no one changed them, they are all broken.


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Old 07-27-2022, 06:18 AM
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Originally Posted by AndreasHannover
Did you cheked the distributor? If no one changed them, they are all broken.


Thank you. I looked at it yesterday and didnt see anything wrong. Well today I took another look and what do you know, I can see the shiny chrome ball at the bottom of it. So thats the problem.

Can I just glue in the bottom part? Does the ball need to move around or can the glue take that on too?

Removing the block I see one screw holding it to the fire wall? And the lines, how I wish I didnt have to take them off. I took many off in my Lincoln days.

Thank You all again. Not that I must have ac out the vents, it would have been fine out the defroster, I mostly drive the car with the roof down. But I love the car and want to keep it forever in hopes of givig it to my son in 12 years when he can drive.
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Old 07-27-2022, 08:32 AM
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Yes, just one screw for attachment.

Mark down or take a picture of how the vacuum lines are attached to the vacuum distribution block for reference.

Just use a dab of epoxy glue or silicon sealant on the vacuum distribution block's crack to seal it.

There is a trick to removing the vacuum lines. Use a 1/4 inch open end wrench to lever between the vacuum tube fitting and the distributor body and they come right out.

The clear line goes back to the trunk pump, See if you can pull a vacuum on it. The red line goes to the vacuum reservoir, see if it holds vacuum. Grey to the engine manifold (no vacuum, but make sure it's connected to the engine). Try them all..

You can start your vacuum pod inspection by taking off the cabin air filter lid and inspecting the vacuum lines for the double vacuum pods you see there and the single one down by the blower motor.
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Old 07-27-2022, 11:23 AM
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Well. Unfortunately gluing the leak did not solve my issue.
Center vent opens briefly then closes. Passenger side vent opens for a bit then closes. Driver side vent works fine.

Defrost and floor works as it should.
Old 07-27-2022, 11:53 PM
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Originally Posted by tbilisi79
Howdy.
Wondering what you guys think about this.
For two years the passenger side vent never had flow in open or closed position.
Now the center vent started going in and out. The vacuum connection is fine behind the engine and playing with the center roller it would blow well in open, but now in closed position too.
As I started to take out the center vent, the passenger vent came to life first time in 2 years. So i know its the rollers.

I took it apart and all


I see is some corrosion on the board.

Any ideas what to do here? I suppose a used one from ebay would work, but who knows what the condition of that will be. Id hate to prop open the center vent open manually as everything else works great.
I couldn't help but notice but what guitar do you have? I'm playing a Duesenberg Alliance Starplayer.
Old 07-28-2022, 06:43 AM
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Originally Posted by BenzBopper
I couldn't help but notice but what guitar do you have? I'm playing a Duesenberg Alliance Starplayer.
Ha... Its a Epiphone Les Paul.
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Old 08-07-2022, 12:54 PM
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A bit of an update.

Yesterday went for a drive, turned the AC on in the parking lot. center vent worked. Once I started going, all sorts of noises in the dash and center vent closes.

Today, Center vent blows perfectly with the center being in closed position. Thats after checking rollers and their voltage working from open to closed.
Passenger vent closed no matter the position.
Go figure.
Old 01-31-2024, 10:23 PM
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Hey Tbilisi,

I sent you a PM but don't know whether you saw it. I have had almost the exact same issue with my '99, and been struggling to solve it. Did you ever find a solution?

My left vent stays shut, but if I swap the lines on the Y11 with the right vent then the symptoms also swap. My center vent opens and closes at random (not in any way related to engine speed). A new discovery I have made is that with the key out and "REST" mode on, my vents seem to function perfectly with the rollers, which leads me to believe that the vacuum to the vents is fine. If I open the center vent with REST mode on, then turn on the key (without even switching on the motor), my center vent will shut and as will my left vent. I have tried a new Y11, a known working HVAC module, a new vacuum distributor, and even another vent / roller unit but nothing solves this strange issue.

What baffles me is that the left vent requires vacuum to close, so why on earth would it be staying shut if there was a loss of vacuum in the system?


Old 02-01-2024, 12:20 AM
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Just replace your vacuum block
Old 02-01-2024, 12:21 AM
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Originally Posted by Ahmed
Just replace your vacuum block
I have replaced the Y11 and the vacuum block
Old 02-01-2024, 12:26 AM
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I was responding to the thread creator @tbilisi79

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