A/C center vent wheel question
 

I recently purchased a used 1998 E320. Now that it is getting dark earlier, I noticed that while the A/C side vent control wheels light up, the center one does not. Is this normal?

In all of my other past and current Benzes, the center vent control wheel also lights up.

If it is supposed to light up, how do you replace it/fix it?

Also, while I am at it, are the buttons for dimming/brightening the lights (on left hand side of instrument cluster) supposed to light up at night?

thanks for your answers.