that's what I didn't get... here passenger and driver have their own, individual and separate, thermostatically controlled vents / areas... as standard.

I see that in many newer cars. I don't know too much about the difference between US and Euro versions, but is it a simple matter of region, or are those differences model dependent?

Euro console from my last W124, arrowed the passenger and driver thermostatic controls.

edit, this was a 1986 W124 E300D

Attached Thumbnails

 

it's a matter of region. i have an '87 300TD and an '89 230TE (euro import) and the '89 has the european climate control with the two temperature wheels. as i understand it the ACC system (with the pushbutton controls) that we got standard in north america was optional equipment in most other markets.

by the way, the centre vent doesn't blow hot air in the european climate control system either so your mods would be applicable to that also, but there would be differences for sure in how it would be done. can't say how different. i don't think the european system has the changeover manifold for one thing and the air direction controls are manual.

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punkinfair

Thanks. I wont do anything drastic I'll try the drill method on a parts car first. #2 will be good enough until the vacuum pod breaks. I have a crack free dash in parts car to try out one day. Hopefully i'll remember to pull that center flap before i install.

I do love the switch. What a great option to have. Man that Euro W124 climate control panel is beautiful. MB realized that in US a lot of rich people wil pay thousands of dollars a year fixing little **** on their cars and exploit that fact. Our local MB Indy is rich rich. MBs are cash cows for him.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

As soon as I finished this write-up, I started playing with that switch that I gave up on... the rear window screen switch (124-821-04-51) with the icons that look sort of like upper and lower vents.




It dawned on me that it wouldn't be too hard to make the rocker stay in the upper and lower positions. I took some cues from the way the other switches do it.

Basically, like many other switches, this switch has a ball bearing in it that is under pressure from a spring. The ball rests in the low point of an internal vee shaped brass rocker. When the outer plastic rocker is actuated, the ball is pushed up one of the sides of the brass rocker, compressing the spring and increasing the pressure on the ball. When you release the switch, the pressure from the spring makes the ball return to the low point or center point in the switch, returning the rocker to it's central position. When the switch pushes the ball up the side of the rocker, that rocker pivots just enough for the tops of it to make contact with a metal post, closing a circuit.








The way to make the switch stay in one of the actuated positions is to keep the ball from sliding back down to the bottom of the vee. This is easily done by drilling a small hole in the side of the rocker for the ball to rest in. A 5/32" hole is just big enough to overcome the spring's pressure, and not too big to make it hard to get the ball out.






The inside of the switch actually has two of these vee shaped rockers and two ball bearings.




There are two separate small metal plates, one under each rocker with an upward bend that makes contact with each rocker. These upward bends are the pivot points for the rockers. On one side of the switch this contact is just to the right of center of one of the rockers, and on the other side of the switch this contact is made just to the left of center of the other rocker. The fact that these contacts are made off center makes the two rockers tilt in opposite directions.






I bring up this detail because when we drill holes in the arms of the rockers, the hole has to be above these pivot points. Otherwise there will be too much play in the switch when the ball bearing is "resting" in the hole - resulting in inconsistent contact between the rocker and the metal post. In fact, it's actually best to only drill one hole in each rocker, and locate that hole on the side of the rocker that doesn't contact the pivot point. Since the pivot points for the two rockers are on opposite sides, there will be only one hole to lock the ball bearings in place in each of the two switch positions (up and down). While one ball is locked in place, it will be the other ball on the other side of the switch that is pushing the brass rocker over the pivot point - making contact with the metal post.






This switch has to be wired differently than the interior dome lamp switch (124-821-02-51) I used in the write-up. Here's a new schematic:




Much Better!

Great documentation job. Personally I would like to fix the air recirc if anything. Drives me up the wall that it turns off after 15min. I would love to see it cycle open every 15min to get fresh air in but then come back to recirc until the button or car is turned off.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Yeah, that would be nice. What about repurposing the recirc switch to manually turn on a vacuum relay that engages the air recirc pod? That way, you could just leave the ACC out of it.

I think this is a very good writeup - thank you OP. As far as the criticism, you all don't have to do it to your cars if you don't want! The OP is happy with his work, and I'm sure those who tackle this will also be happy which is what matters. Well done!

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

A well written DIY, thank you for spending the hours writing/editing it.


This DIY has been sent to webmaster@peachparts.com for the PeachPartsWiki





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Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
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1985 300SD
1983 300D
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This DIY is now in our Wiki HERE.
Thanks!

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Bill Wood - Retired Webmaster
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1998 Mercedes E430
2010 Toyota Sequoia
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That looks great.

Webmaster, thanks for adding this to the wiki! That's been an invaluable resource for me.

BTW, you might want to re-save the original graphic for the schematic as a GIF. Non-photographic images like that one don't hold up so well to the JPEG compression. It's a bit hard to read some of the numbers.

Done!

- Changed schematics to GIF

- Added Addendum to include "rear window screen switch" info

__________________
Bill Wood - Retired Webmaster
My Personal Website
1998 Mercedes E430
2010 Toyota Sequoia
My Photo Albums

Thanks everyone for the positive comments!

It is weird that something like the climate control would be intentionally engineered differently for specific locations. The climate of Europe isn't that different from the US, and we both have a wide range of conditions throughout the seasons. Besides, it's not like us Americans need our climate to be controlled differently than citizens of other nations. We're all humans. I'd love to know what the specific reasoning was behind a decision like that.