I didn't know there was a bulb on mine (93 W124) until I went to replace the headlight switch for another problem...upon removing it, there was a wire with the bulb attached to it...so I replaced it and VOILA! Now I have backlighting for the headlight switch!

Curious why the C-class wouldn't have one...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car