I just purchased an 1989 300E and I have everything working now with the exception of the center air vents in the dash. I removed the glove box and found where the vacuum hoses attached and they all are attached and look fine.
Any help would be grateful.
Thanks

You need to apply vacuum to each of the 7 lines behind the glovebox. If any won't hold vacuum, that pod is bad. Your center vent pod is probably toast - very common problem. Replacement of this $25 part takes 6-10 hours for a first timer - it's a huge job. A simple band-aid fix is to swap the vacuum lines for the center vent & diverter - switch lines #4 and #6 on the 7-port manifold. This will at least allow cool air to exit the center vents, although the airflow path through the heater box is not optimal.


For more info on the whole procedure, go to this thread:
W124 climate control vacuum pod replacement

For photos of this exact job being done on my car:
http://www.meimann.com/images/mercedes/W124_dash/



Good luck!

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For some reason I seem to recall that the center vents work only for specific functions. Possibly air only or heat only.

You might want to check idea out. If so your climate control wheel might also have to be fuctioning properly because it determines if you get hot or cool air... that is on the 300E.

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Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

Center vents should blow cool air only - never heat. You check the pod by applying vacuum to the vacuum line for that pod. If it works correctly, the problem is electrical - but that is extremely unlikely. Trust me.

:p

I tried switching lines #4 and #6 on the 7-port manifold and still did not get anything to come out of the center. I also tried all settings/switches on the panel. It seems like I am getting ac through the defrost on most settings and do not think it should be on all the time.
Thanks

Hmmm. It's time for more troubleshooting then. Check if you have vacuum present at the inlet to the 7-port manifold, the line that comes from the engine compartment. If there is no vacuum, find the disconnected or broken line and fix it. If you DO get vacuum there (with the engine running), the problem is probably electrical. The default position of the flaps is full defrost, as a safety feature. The defrost flaps should close completely when the ACC is set to full cold, and the center vents should open. On full heat the center vents close, the defrost vents open partially, and the footwell vents open. The factory climate control service manual actually has some very good diagrams and troubleshooting information - you might want to read up on that. (If you don't have the factory manual, drop me an email or PM.)

I have vaccum at the manifold, not alot but not sure how much it should be (used the finger over the end of hose tester).
I just purchased a 2 cd service manual from ebay and the wiring diagram pdf is the only one so far that would not open, any help would be great.
Thanks

If you have a gauge, you should be getting at least 15-20" of vacuum. If you feel anything at the hose, it's probably OK. Sounds like the problem may be electrical. The wiring diagrams is not what you need. Look for the climate control (ACC) section. This mostly points to a bad pushbutton unit, or less likely, some bad temp sensors. You *have* checked all the fuses already, right...?

All the fuses are good. In the ACC section I cannot find a diagram relating to mine, built 11/88. The ones I show for a 124/30 are 87 and prior (I bought these cd's why?)
All the switches seem to work i.e. something turns on or off or increases or decreases fan speed.

I also have had both of these symptoms on my 89 260E.
For the defrost vent on with A/C, I found I had a bad vacuum pod. Mine has two separate parts to it and only one half was bad. The result was the defrost vent was left partially open. While waiting for the part, I disconnected the arm from the pod and moved the vent control arm manually to close the defrost vent. Replacing the pod fixed all that of course.
My center vent also does not work. I can see the what I think is the center vent pod up on top of the air mainfold through the glovebox opening, but cannot reach it. I am wondering if it can be accessed by removing the instrument cluster. Another post said it would take 10 hours for a beginner. (So that would be me in that I have never removed a dash before.) Is that really the only way to get to the pod?
I am really interested in anything on how to replace the center vent pod.
John

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John
89 260E 236,000 miles
97 E420 106,000 miles
87 Volvo 765 312,000 miles
07 Volvo S40 T5

Well tonight it actually got cold enough to turn on the heat in the car (can you believe it was cold here in Arizona....) Anyhow, the next thing I know there is warm air coming out of the center vents. Now I am totally confused as I thought nothing should be coming out of the center since they dont work for a/c or vent.
I wasnt able to borrow a vaccum pump to check the lines yet to see if the center pod is bad.

John,

The pod you can see up top is the diverter pod, NOT the center vent pod. Look at the photos in my link above, that shows you where everything is. Pulling the dash is the ONLY way to access the center vent pod. If you just want cool air out the center vents in the summer, switching the #4 and #6 vacuum lines will work as a temporary solution - I drove the car like that for 2 years before fixing the center vent pod. It was better than the "wind tunnel" with 100% of cold air coming out the two end vents...!

OK - that's weird. You should not get any heat out the center vents ever, even with the #4 and #6 lines swapped. You WILL get some air out the center if you have the temp wheel in the middle and the system thinks it's too warm inside, but it should be cool air, not warm.

I really think you have a problem with one of the temp sensors, or the ACC pushbutton unit. What you describe is not a vacuum problem (although it would be good to test the vacuum pods anyway - probably at least one is bad.)

gsxr,
Thanks. I will get out the mightyvac to test all my vacuum lines as is being suggested to azgator. (Going to buy one today.) You say to swap line 4 and 6. Are they numbered from the top? Is the vacuum input line considered #1. Is there a printout of the 7 port manifold outlet definitions anywhere? I also read a reference to an ACC service manual. Can you suggest a CD set to buy that has all of this? Would it include information on how to remove the dash?

I know an awful lot of questions. Sorry. I'm stuck here and want to get this fixed before next summer. I am sure azgator has the same problem in Phoenix as I do in Houston during the summer. (I just don't have the "dry" heat.)
I downloaded all your pictures. That is a help, but it sure looks like a lot of work as you indicated.
I really appreciate your reply. I don't mean to hijack azgator's post, but hopefully this will be helpful to him also.
Thanks. John

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John
89 260E 236,000 miles
97 E420 106,000 miles
87 Volvo 765 312,000 miles
07 Volvo S40 T5

Hi John,

If you buy a MItyVac, try looking for the Silverline 4050 kit which is the metal-body pump that also does pressure testing (very handy on diesels). Anyway, no, the top vacuum feed line doesn't count. There is one input and 7 outputs, top is #1, bottom is #7. I think it's printed on the side of the manifold along with the color codes for the vac lines. The ACC manual has great diagrams for this. About the service CD, check your email/PM...