I've got an '86 300E w/only very weak airflow to the front footwells, I assume they are not opening up. As far as I can tell, everything else in its climate controls functions as it's supposed to. Turning the fan up higher will give noticeably more air to the side vents if they're opened, or to the windshield, if side vents are closed. I think the rear seat floor vents are getting (somewhat) more airflow than the front footwells...

I did check the center vents btw, they get strong airflow when A/C is turned to Min. But my feet are Cold driving this car w/the heat on- what's the likely culprit here?

I also wondered if the footwell vents can just be forced open easily in the meantime, for the winter months.

In case this means anything, my fan speed pushbuttons do not always work right when first starting out in cold weather, then they "loosen up" as things warm up and function normally.

I posted this Q in this older 5-pg thread, but I'm not seeing it bumped up : http://www.peachparts.com/shopforum/diesel-discussion/35373-w124-climate-control-vacuum-pod-replacement-post1025460.html#post1025460

This definitely sound like a leaking vacuum servo. I have the same car as you and I had the same problem about three years ago. Each side of the floor vents is operated by its own vacuum servo however they are powered by one vacuum line so if one of the servos rubber has cracked and is leaking air both sides will not function... Simply take apart the center console (you are trying to get below and behind the radio) and the unit takes two minutes to replace... I picked up a used one from a wrecking yard and it has worked for the past three years. In the meantime you can jam some sort of object in the floor vent to hold it open and keep your feet from freezing. Good luck!

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05 E55
03 E500

Thanks JFAZ- I'll check that out.
I think climate control -even when 100%- is the worst-designed thing about the w124.
Hope your car feels the same way mine does, which is, aside from the little pita systems needing attention from age, that it could run forever.

I HATE THE CLIMATE CONTROL ON MY 124! best of luck to your repairs, its a good weekend project

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05 E55
03 E500