You may need to pry the knob off with a small screwdriver (put some cloth between the screwdriver and the console)
heres a link with a pic PeachPartsWiki: Heater Control Dashboard Light Replacement
the lamp is behind the small metal flap, and I hard a hard time removing the lamp and holding the flap open
so I ended up putting superglue on a toothpick and gluing it to the burned out lamp to pull it out.
be sure to remember the alignment on the dial & you may want to replace both lamps at the same time.
I used a Sylvania #2721 lamp
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!