Mercedes-Benz C-Class automobiles come standard with turn-signal indicator lights on the wing mirrors. The light in question is an LED, most easily procured from an authorised Mercedes-Benz dealer. Changing the lamp can prove difficult if you are unfamiliar with the design of the mirror, but with a little patience and care this is a repair easily achieved in the driveway.
Fold back the mirror so it lays flat against the vehicle.
Locate the small opening at the rear of the unit visually.
Insert the screwdriver into the opening gently, feeling for a small metal tab located a short way inside the mirror.
Press the tab gently with the screwdriver toward the vehicle, taking care not to use too much force. The mirror will become free as the spring tab releases its tension on the unit.
Pull the mirror slowly back toward the rear of the car. The mirror housing will slide off the unit.
Remove the old bulb carefully. It should be retained for reference should the process need to be repeated.
Insert the new bulb into the socket, gently pressing until it is secure.
Slide the housing back toward the front of the vehicle.
Press the unit until the spring-tab clicks back into place. The mirror should again be secured to the vehicle.
Check to ensure the housing is indeed secure and that the replacement bulb is functional before driving.
Always use care when preforming delicate tasks with your vehicle. Haste can cause damage, turning a small DIY job into one requiring a mechanic's attention.
Never perform repairs on electronic equipment in damp, rainy or otherwise humid conditions. Never perform repairs on a vehicle while it is running.