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post #1 of 23 (permalink) Old 03-20-2017, 07:22 AM Thread Starter
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AC Center Vent question

Hi,

As per many others, my center vents are not blowing cold air.

I've run through the diagnostics, and cleared the old error codes. All sensors check out fine.

I wanted to test the pods on the center vents (I know the defroster flap pod is working).

Does anyone know which color tubes go to the center vent pods?

Cheers
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post #2 of 23 (permalink) Old 03-20-2017, 08:46 AM
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Scottpetrd, some where there was a test method for "exercising" the pods one at a time from the climate controller. It was on this forum but I didn't go through with it because my mechanic said: If you never use certain pods and you actuate them and they stick open, what now? And since that time on I lost interest. I have noticed that unless you turn on the center blue switch you don't get much air through the center vents. However, I've also noticed that the car just gets warm or cold depending on the settings. Seems to work completely different than other models. Just a gentle warming or cooling of the vehicle with no fuss or air blowing in your face.
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post #3 of 23 (permalink) Old 03-20-2017, 10:37 AM Thread Starter
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I've been looking for that test procedure. But all I've found so far is for the later models with the digital climate controller, not the early dial-based on like I've got.

I'll keep searching.

I may have to re-up my subscription to AllDiYData
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post #4 of 23 (permalink) Old 03-20-2017, 01:20 PM
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this was written by a forum member many years ago. it is ok for 1991 car:

1. Start engine, press left and right AUTO buttons on a/c controller and fully open all vents with thumb wheels.
2. Press REST and C/F buttons together and hold for at least 5 secs. Left display will show 0 and right display LO. I think all flaps should now be closed, except I get a small amount of air from the far left and right vents.
3. Press right AUTO and right display will now show HI. I think that all vents should now be open except the defrost (in my case).
4. Press left AUTO button. Left display will show 1 and right display LO. Etc, etc.

As you proceed, the right AUTO button opens and closes the flaps corresponding to the number displayed in the left display. The left AUTO button changes the flap selection, starting at 0 and ending at 15: it then cycles round again. N.B. LO does not always correspond to a closed flap and HI does not always correspond to a fully-open flap - very confusing.

The rest of the information that I have is very lengthy and contains many errors, as far as I can tell. But briefly:

#1 & #3 = left centre outlet (#3 also activates the left blend flap)
#2 & #4 = right centre outlet (#4 also activates the right blend flap)
#5 = far left & far right outlets
#6, & #7 = left defroster flap
#8 & #9 = right defroster flap
#10 & 11 = main air flap and recirc flap
#12 & #13 = left footwell outlet
#14 & #15 = right footwell flap

I don't know whether this will be of much assistance to you but at least you maybe able to exercise the system. I believe that Alldata has the full info.

I guess that you could also try the above while examining the switchover valve: you might at least be able to check that all the valves are doing something.
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post #5 of 23 (permalink) Old 03-20-2017, 09:18 PM Thread Starter
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Samo,

Thanks so much for this. I'll check it out today.

I've been looking at diagrams I've found on the net. It appears that the piece I see on the lower part of the passenger's footwell is NOT the Y11 valve that controlled by the climate control computer (N22), but rather the vacuum valve block (#36) for headlights, etc. That's from the 'locations' diagram below.

The Y11 block is apparently higher up on the firewall, and I have to remove the passenger's airbag to get to it.

What is unclear to me from the diagrams is where the vacuum reservoirs (#1, #3) are located. Are they inside the car in the footwell, or up inside the passenger fender, between the body and the wheel well liner.

This is from McMahon's legendary thread on this vacuum system.

My understanding, at present, of how to diagnose this:

- Make sure I have vacuum from the intake manifold to the grey line on port 7 of the vacuum valve block, as well as vacuum assist from my newly rebuilt PSE on port 7.
- Make sure I don't hear any leaks from the vacuum valve block
- Make sure I have vacuum on port 5 of the vacuum valve block that runs to the Y11 valve block.

Once these are confirmed, then I can run the flap test.

What I'm a bit confused about is: as I have cables from the dash-mounted thumbwheels (and yes, I have already pulled this, and found that the cables had been disconnected by the PO), why would I need vacuum actuators on the flaps. Would not the cables actuate the dash flaps directly?


But just in case, I did purchase a set of actuator pods on ebay yesterday (A/C AC BLEND FLAP VENT MOTORS ACTUATORS Mercedes W140 92-99 S320 S420 S500 S600 | eBay). I hope these are the correct ones for what I have. They say they are for the cable operated vents, which is what I have.

Cheers and thanks for this help. As soon as the morning monsoons stop, I'll go out and play around some more.
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post #6 of 23 (permalink) Old 03-21-2017, 12:14 AM
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Quote:
I've been looking at diagrams I've found on the net. It appears that the piece I see on the lower part of the passenger's footwell is NOT the Y11 valve that controlled by the climate control computer (N22), but rather the vacuum valve block (#36) for headlights, etc. That's from the 'locations' diagram below.
i played a lot with this stuff, so i know something about it . You are right. valve block at the passenger footwell is not controlled by N22. The switchover valve Y11 is controlled by N22.

Quote:
The Y11 block is apparently higher up on the firewall, and I have to remove the passenger's airbag to get to it.
do not touch airbag. just remove the glove box and you have a good access to the valve. I removed it without a big drama and opened whole assembly. I found no faults so i mounted it back. Not a big work at all.

Quote:
What is unclear to me from the diagrams is where the vacuum reservoirs (#1, #3) are located. Are they inside the car in the footwell, or up inside the passenger fender, between the body and the wheel well liner.
i only have one reservoir. but there is only extremely small chance that something is wrong with it. in my car it is behind the wheel liner (right front one) like you suggested. no big deal to get access. so you work from outside only to get it.

Quote:
What I'm a bit confused about is: as I have cables from the dash-mounted thumbwheels (and yes, I have already pulled this, and found that the cables had been disconnected by the PO), why would I need vacuum actuators on the flaps. Would not the cables actuate the dash flaps directly?
do not be confused. this is just as it is. you can manually open/close center and side vents. system with cables enables a control by people in the car. controlling of flaps should not depend on people in the car so engineers did it over pneumatics and N22. the cables control opening/closing right at vents. Everything what is controlled by pneumatic flaps is on the HVAC unit itself, so one can say that cables are part of the car, and flaps are part of HVAC unit (the monster which can be accessed only if you remove dash, console, etc.).

All I wish for Christmas is a smooth idle.
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post #7 of 23 (permalink) Old 03-21-2017, 04:07 AM Thread Starter
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Samo,

Large success today. All thanks to you!

I started with the flap control diagnosis. All flaps failed. Only outlet working was the defroster. So, either I had a leak in one of the control pods causing the system to lose air, or, I had no vacuum to Y11 to begin with.

So, I started by focusing on the Y7, the vacuum distribution block. I first made sure that I had vacuum from the engine (the grey line on port 7). I had 15" of vacuum. Great. Then tested the clear line running from my newly repaired PSE. Variable vacuum.

So then disconnected a random line from the block, and tested the vacuum coming out of the block. Nada. Zilch. So, I had a leak somewhere.

One by one, disconnected the lines and checked them to see if they held pressure. Lines 3 (headlight range input), 9 (headlight range output), 12 (at resevoir), and 13 (ac resevoir) all leaked. So, I blocked off the ports on the block for the leaking lines (except for one) and tested to see if the block held vacuum. Nada, zilch. So, my vacuum distribution block is bad.

Next up: Jumpering. Tee'd together the grey line from the engine, the clear line from the PSE, and the grey-green line that supplied vaccuum to the Y11 valve. So now the Y11 was being supplied a known supply of vacuum (sans reservoir).

Turned on the engine, put the system into Auto mode, and fell out of the car! For the first time since I've had the car all the vents work!!!!

So, I then ran through the flaps test you so helpfully provided. All vents tested fine. So none of my control pods leak (so far. now that they are going to be used, I'll have to wait and see). I de-ox'd the electrical connector to Y11 while I was in there.

I've found a block (140 830 0485) on eBay and have ordered that.

So, two issues here.

1. Have to pull the wheel well liner and see why the resevoir is leaking. My money is on a disconnected line.
2. Should I put a check valve in-between the engine vacuum and the PSE vacuum? Common sense says to do this.

Again, I could not have done this without all the fantastic information you have provided. I think you should be lauded and notated as THE expert of the ventilation systems for these cars!

Cheers
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post #8 of 23 (permalink) Old 03-21-2017, 05:43 AM
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Individual flap test for pre-facelift is, also, described in manual.startekinfo.com;
STAR TekInfo

It even has a detailed function test and what to check in the center vent to blow cold air;
http://manual.startekinfo.com/manual/JSP/cc/3_2/m11.jsp

And pictures of the vacuum system;
http://manual.startekinfo.com/manual/JSP/cc/3_2/m33.jsp

br,
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W123 230E 1984

Last edited by syljua; 03-21-2017 at 05:46 AM.
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post #9 of 23 (permalink) Old 03-21-2017, 07:40 AM Thread Starter
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Syljua,

That's fantastic. Thanks for these.

Now, as to the source of my vacuum leak. I pulled the resevoir out of the fender well. This is what I found.

I know the red line runs to the vacuum distribution block. But where does the black line run? There is no vacuum lines in the fender well that I can attach these to.

Cheers
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post #10 of 23 (permalink) Old 03-21-2017, 08:48 AM
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Quote:
Originally Posted by scottpeterd View Post
Syljua,

That's fantastic. Thanks for these.

Now, as to the source of my vacuum leak. I pulled the reservoir out of the fender well. This is what I found.

I know the red line runs to the vacuum distribution block. But where does the black line run? There is no vacuum lines in the fender well that I can attach these to.

Cheers
I too have spent some good time troubleshooting vent problems, and generally it starts from that vacuum storage box. Then to the manifold block in the passenger kick panel, and then the PSE...

What I encounter here in the Western USA is the no center vents is PSE leak, and then to the block in the kick panel. The block in the kick panel will leak from the ball bearing plug as the plastic will split...See photos of the block...

One vacuum storage box line goes to the engine/ on older W140's have this terminal visually seen around the top of the blower. The other line goes to the distribution block in the kick panel.

Hope it helps,

Martin
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