None of the switches for the climate controls light up at night. It's not that big of a deal to me, but it'd be nice if they did light up. Also, only the defrost switch lights up... the antenna, rear dome light, and sunroof switches don't light up. Any ideas? Is this a complicated fix?

Hey Speedy,
Don't feel bad about your dash lights, i have the same problem. One thing about M-B's dash lighting is that IT SUCKS! All of my dash lighting works except my climate control, and from what i have been told on this forum, its a pain in the a$$ to change these bulbs, in fact i don't think ill ever change them myself. Your other bulbs on your defog. sunroof etc. are much easier to fix. Simply take out the entire switch with a very fine screwdriver taking care NOT to chip the wood. The bulb is within the switch if im correct. The Haynes service manual provides excellent pic's for this job. Dont try to pop out the climate control panel like the other buttons, it dosent and you will chip your wood. The dash lights have to be changed up and behind the climate control panel, very difficult.
Look back and you should see my post with this same question.
Good Luck

Its not that difficult on a 123...
 

Take off the wood panel that surrounds the climate control buttons. Then unscrew the black climate control package 2 screws, the third holds on something else. Pull this out and look agains the back wall. You will see something that looks a little like an octopus. In the center there is one lightbulb, going out the sides are little black wires, that are actually fiber optic, and go to the switches above. Either the bulb is burned out, or somehow the wires came undone. While you have the black plastic box in your hand, (the one with all of the buttons), you can check it for burnt bulbs too. There is one that can get rather warm, and slide out of its spot.
Hope this helps.
-Larry

Should the temperature wheel be illuminated? My buttons light up, but the wheel doesn't.

Yes, the temperature wheel *should* light up. But mine doesn't.