My W140 was missing some lights in the air condition control unit. The temperature dials and display was completely dark, making it impossible to control the temperature at night. This was what it looked like in the dark, the temperature dials are beside the “auto” buttons.
I bought 10 new bulbs on ebay and checked the procedure described in the official workshop documentation before I went to work.
First step is to remove the “Auto” button. It simply pops out, so gently pry it out with a flat bladed screwdriver or something similar.
You can see the white plastic cap, pry this one loose as well with a flat headed screw driver
And then the bulb is visible deep in the hole beneath the cap. Use a pair of tweezers to get it out
Put in a new bulb with the tweezers, put back the cap and the button, and you are finished. Looks a lot better in the dark now!
Next step is to replace the bulb for the fan dial, but to do that you must remove the wood trim first. I am going to do that another day, and buff and polish the wood when I have it removed from the car at the same time.