Replacing the headlight on a Mercedes-Benz C-class is something you can do yourself with a few basic tools and a little patience. The parts needed are accessible at any auto parts or repair store. Doing it yourself will save you the time and money of having to take the vehicle to a mechanic. The headlight bulb can be replaced entirely by hand.
Open the bonnet and locate the back of the headlight with the faulty bulb. Remove the electrical connector from the headlight. Work it free using a gentle side-to-side twisting movement and slight force.
Turn the bulb holder counter-clockwise one-quarter turn. Remove the bulb and bulb holder from the housing by pulling back and out.
Remove the old bulb from the bulb holder by turning counter-clockwise. Insert the new bulb, locking it into place, by turning clockwise.
Replace the bulb holder into the housing. Turn clockwise to tighten. The bulb holder will click when it is locked into place. Plug the electrical connector back into the rear of the bulb holder.
Turn the lights on to test the bulb.
To save time in the future, replace both headlight bulbs at the same time.
Wear gloves when handling the bulb. This will avoid oil and grease contamination from your hands, which can reduce the bulb's life. Check that both headlights shine equally bright. Often a new bulb will shine brighter than an old one. If this is the case replace the other bulb, too.