Headlights MERCEDES-BENZ C-Class Saloon (W205)

Hey! You're not the only one who's run into this issue with replacement headlights on the W205—plenty of owners find that only the daytime running lights (DRLs) work while the rest refuse to join the party. If Mercedes says “no” to the headlights but the VIN checked out, here’s what fellow owners and techs would look at first:
- Headlight wiring & connectors: The W205 headlight plug is a multi-pin connector, and the wiring diagram for these is a real puzzle. Each major function (DRL, indicator, low/high beam, etc.) gets its own wire and sometimes a different control signal, depending on the car's options and year! If only the DRLs work, it's probably an issue with the control module not communicating properly with the headlight—in other words, it might be a coding issue, not just “plug & play”.
- Coding: Unlike older cars, the W205 often needs the headlight “coded in” using Mercedes STAR/Xentry or a pro OBD tool. If you swap a non-OEM or aftermarket headlight—even if it’s VIN-compatible—your car’s control unit might not send power to anything except the DRLs until it’s told “yo, this is my headlight now.”
- Headlight control module: On Mercs, especially with LED or Multibeam lights, there’s a module (“ballast”) right under the headlight that actually talks to the car’s ECU/body control. If yours isn’t the original (or is mismatched), you might need to swap modules or check wiring for power/ground to all pins, not just the DRL circuit. And if water got into the previous headlight, it sometimes fries the module and that breaks communication with the new light.
- Compatibility gremlins: Even if your VIN matched, sometimes the internals are different for cars with high-tech options (adaptive or Multibeam) versus standard. So a part can “fit” but not function fully.

You can check the wiring absence of power on those pins with a multimeter, but most folks end up needing a dealer or specialist to code the headlight once the wiring is confirmed good.

Do you return the headlights? Not yet! Confirm wiring, talk to Mercedes about coding, and if the module needs swapping, sometimes you can move it from your old headlight (if it wasn’t the cause of failure). Usually, replacement with correct coding sorts it. If not, your seller should take the item back under compatibility guarantee—just be armed with the facts!

Good luck—don’t panic, this one's a common Merc riddle, not your fault!