1987 w124 300D but applies to lots of climate control systems like it, I'm sure.

Has your climate selector button operation been degrading over time? Maybe to the point where no buttons stay selected, or pop back out on their own after some minutes. Are you holding in buttons as you drive to keep a function (like defrost, or high fan) selected, like me? This was getting ridiculous! I had functions, but as soon as I let go of the button the function deselected itself. I also noticed button travel was getting less and less, as if all buttons were always almost selected.

Problem: there are at least two styles of plastic cages that the climate circuit board sits in. One style is one-piece bonded with the front panel, the another style is two-piece that allows the circuit board box to be snapped apart from the front panel. The problem for me was with the two piece style. Only four rather flimsy plastic tab/clips hold the rear circuit box to the front panel. As these tabs break over time due to stress of pressing buttons, it allows the rear box to drift away from the front panel deeper inside the dash. Finally, when all tabs break the rear box is only held to the front by only the push buttons themselves.

I found four places to sink a few tiny screws into these two parts to hold them back together. You have to be very careful picking spots to drill, and use screws of the right length, to avoid interfering with button movement paths inside. I picked a couple spots at the top right beside broken plastic clips, sunk them in from the front. And two spots up from the bottom, drilled between the two outer-most pairs of buttons on each side.

Once the face plate and box are joined again like this, every button push is positive again, clicks into "on" and pops out perfectly when another is selected.

Whole job about 1 hour including R&R on 1987 300D.

Hope this helps at least one other person.

__________________
Cheers!
Scott McPhee

1987 300D