Ready to take the dash apart... - PeachParts Mercedes-Benz Forum

sublettm · #1 02-18-2003, 08:36 PM

Ok guys,
I asked the question a few months ago and received great input about how to replace the valve that controls air flow through to the center vents. You all posted great pictures and all, but what is the exact name for the part needed. I have searched all of the threads on this topic and tried every name mentioned for the part in question, but get no results when searching on Fastlane. I looked in the performance products catalog and the part is not listed in their parts breakdown.

I am ready to tackle this project now that "winter" is just about over here in Houston. My wife would really appreciate it if I had this problem rectified before our first day in the 90's.

Actually I have to tackle this project on both of my cars...oh joy! If someone can give me the name for this part, or the fastlane part number, I would greatly appreciate it.

Mike

speedy300Dturbo · #2 02-18-2003, 08:47 PM

You need the vacuum element for the center nozzle, the part # is 116-800-11-75

VeggiePup · #3 02-18-2003, 08:55 PM

Like he said.

I removed the dash from my '83 300CD last summer. Twice. Thought I would try to fix the element. How stupid! The repaired element worked fine until I reinstalled the dash, then it failed. Removed the dash again the following week to install the new element. A/C is much better now. Of course, Little Rock isn't like Houston....

sublettm · #4 02-18-2003, 08:57 PM

Thanks for the quick reply. I am dreading this task, but I guess I will enjoy it this summer once the temp gets into the high 90's.

Mike

fz500sel · #5 02-18-2003, 10:09 PM

Supposedly there is a screw that holds the center console assembly to the dash, but it is not visible. I just about had the dash out but as I pulled on it the center console wanted to come with it. How do you get to that screw? The CD-rom was NO help at all. The car was my '85 300D.

sixto · #6 02-19-2003, 02:19 PM

I'd recommend you check all the actuators before taking the dash apart or certainly while you have it apart.

You can get replacement diaphragms for $5. I'm not sure if FastLane carries them. Someone mentioned earlier that a repair didn't last. I don't know if the repair included a new diaphragm.

On a 126 the dash doesn't have to come off. Even the element doesn't have to come off. You pop the lid, cut out what you can of the old diaphragm and fit the new diaphragm. Takes some fiddling to get the lid back on properly if the actuator is not in your hands but it can be done.

Again, on a 126 it's behind (ahead?) of the push button unit which you can definitely get to without pulling the dash. Might not be the case on a 123.

Sixto
91 300SE
87 300SDL
83 300SD

gsxr · #7 02-19-2003, 02:35 PM

The diaphragms are available from Performance Analysis (George Murphy). Please note that the kits DO NOT work properly for dual-chamber pods, i.e. defrost and recirc pods. It should work for the center vent pod which is a single-chamber. After messing with these personally on 4 different cars, I recommend only buying new ones unless you enjoy fixing them on an ongoing basis.

For the record, on the 123 chassis I believe you can only repair/replace the center vent pod properly by pulling the dash. The defrost, floor, and recirc pods can be done with the dash in place.

On the 124 chassis, only the defrost and floor pods can be changed with the dash in place. The recirc, center vent, and diverter pods all require dash removal. I posted a detailed thread on this topic, with photos, but can't find it in the site search! How annoying...

sixto · #8 02-19-2003, 05:41 PM

Dave,

What's been your experience with rebuilding the dual chamber actuators? What specifically doesn't work or doesn't last? Is it that the actuators parts don't seal as well the second time?

I 'rediaphragmed' the recirc, defrost and center vent actuators in the SDL and all seems well. Still have a blower issue but I'm sure it's not related. I can't imagine how the center vent actuator comes off a 126 -- I can't get a screwdirver on the screws (there's structure in the way) and I can't get to the business end of the lever without pulling the dash (no mention of pulling the dash in the manual). The rest of the actuators are cake.

Thanks,
Sixto
91 300SE
87 300SDL
83 300SD

gsxr · #9 02-19-2003, 06:29 PM

Sixto,

The repair kits for the dual-chamber pods will seem to work, except that the travel is significantly reduced. If a new factory pod moved the shaft 1.25 inches total, after rebuild it moves about 0.5 inches or 0.75. So whatever flap it's supposed to move isn't getting fully opened. I discovered this while testing a freshly rebuilt pod with my MityVac. I re-did it several times, thinking I screwed up, until I finally studied the design enough to figure out what happened.

In a nutshell, the original design has the rubber diaphragm attach to the front of the piston, with a fairly tall side wall of the rubber piece. This allows a long travel. The replacement stuffs into the rear of the piston, and the rubber wall is less than half as tall (!!), resulting in half the movement at best.

IMO, it was a poorly engineered Band-Aid fix. It should NOT be used unless the pod you want to rebuild is no longer available from Mercedes (not likely). Otherwise, to get full movement, you need a NEW complete vacuum pod. Note that the front chamber can be rebuilt, as it uses the same rubber part as the single-diaphragm pods do... but with the pods only costing $25-$40/ea, I say put new ones in and forget about it for the next 10+ years.

Photos of my dash R&R, and photos of the pods torn apart with the rebuild kits, are here:
http://www.meimann.com/images/mercedes/W124_dash/

HTH,

sixto · #10 02-19-2003, 06:55 PM

Dave,

That's good to know. All the inner chambers of my dual actuators were shot so I have no idea how much travel there should be.

Those pics of what's inside a 124 dash will give me nightmares. The 126 is laid out so much more logically from a getting in there standpoint. If you know what you're doing, you can get to the defrost and both recirc actuators (all 3 duals) through the glove box cavity.

Sixto
91 300SE
87 300SDL
83 300SD