I charged the AC system on my '87 300SDL and it now cools well. But there is still no air coming from the 2 center air nozzles. The slide lever is in the open position.

Any ideas how to fix and how difficult of a job is it?

P E H

Check to see if line #4 on the switchover valve (behind glovebox on W124, it might be behind the control panel on your car) holds vacuum. If not, then... you need to probably replace the center vent vacuum element. It requires removing the dash, unfortunately.

On my W124, this vacuum element has failed. Instead of pulling the dash, I removed the center vent nozzles and held the door open with a piece of plastic. Air always flows through them now. The vent can be closed with the slider wheel on the nozzles if I don't need air coming through. This is a good alternative if you don't want to go through the troubles of removing the dash.

Any vacuum leak in the hvac syst. could cause this, the switchover valves in the 126 are on the right side behind the carpeted panel on the side of the console. Most likely culpret is the fresh air door behind the glove box, two double element valves. Get a Mityvac and test for leaks, the supply line for hvac is red with green stripe.
jerryb

JerryB,

What is a Mitivac and where can I get one? I assume it is some type of vacuum tester.

P E H

Yes, it is. Most auto parts/tool stores have them (online and B&M). Some people prefer the metal bodied ones over the plastic? There was an older thread with some really good pricing discussed.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Im curios as to the climate control system as well...I have a 300SDL and I have seen the thread on removing the dash...and I really REALLY dont want to do it. Can there be a minimal invasive way of accessing the elements for theW126? I have a leak in one of the pods if not more.

Three pods are accessed via removal of the glove box.

The center vent pod is the problem. It's behind the CCU in a tough place and there is no way to connect the actuator rod. If you're lucky, it'll be fine.

The footwell pod can also be accessed from behind the CCU.

The usual culprits are the dual pods........main air door and defrost.

I agree with Brian, it is the pod that is behind the CCU. I changed mine out this past summer. It was very difficult to do, I cut my fingers trying to hook up the rod. Once a new pod was installed, I had air out of the center vents again.
The pod is an oblong looking one. Look in the parts Fastlane parts section here and you will see a picture of it. Good Luck!

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John
1986 300sdl
1985 380se

Im gonna take the mityvac to it this weekend...the vac manifold is behind the pax carpet...any color coded vac lines to the different pods?

When you get to the vac manifold, the horizontal legs on the switchover valves go to the pods.

The six switchover valves are numbered from 1-6 starting at the top:

1: Defrost
2: Legroom
3: Center nozzle
4: Scoop
5: Main air door
6: Main air door

The usual culprits are 1,5, and 6.

Heres what I found...all vac lines from this manifold wouldnt hold a vacuum...they all slowly leaked back to 0. #1 though, wouldnt hold ANY vaccum for ANY length of time.

Whaddya think?

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Did you remove and test each horizontal line where they connect to the switches?

It would be inconceivable that all six pods are NG.........I sense a flaw in the testing procedure.

Yeah, I pulled them off and jammed the mity vac into the rubber boot on each one. None of them held a vacuum...although #1 didnt wouldnt even let me pump it up to 15" whereas the others would.

My procedure was starting at #6 and pulled the rubber boot off the manifold and jammed the mity vac on it and pumped it up...it would go right back to 0...the same held true all the way up to #1 where this particular line didnt hold at ALL.

Then I removed the vac source lead in the very top (red line with green stripe) and pulled vac from there...with the ignition on...these were the results...

Defrost = Held vacuum!

Any other setting = vacuum dropped away!

Is this one dill of a pickle or what!?

You should have pulled the vacuum hose from each individual switchover valve........the horizontal leg........and then run an extension hose to each individual vacuum hose.........and then pumped up the Mityvac on each line to see what it holds.

You're not "pulling the rubber boot off the manifold"...........whatever that means........

You're in a pickle because the procedure is just wrong.

more specifically...

From the manifold (the black thing with the numbers on it) I pulled off the rubber connector the connects the vac hose to the manifold and pumped up vac on each line...one by one.

Should I be connecting the mity vac directly to each element...because I was under the impression that these 6 lines go to 6 pods. Therfore, if you pump up the vacuum on each of these 6 lines, you are therefore pumping vacuum to each of the pods.