Mercedes-Benz C-Class and C-Class AMG: Why Won't My Interior Lights Turn On/Off?

Do your interior lights stay on when they should be turning off? If your C-Class or C-Class AMG is experiencing interior lighting issues, read more to diagnose and fix them.

By Tom Cavanagh - June 5, 2015

This article applies to the Mercedes-Benz C-Class (2007-2014).

A car's interior lighting system has certainly evolved since the days when the only illumination came from a single dome light located in the no-man's-land between the front and rear seats. When you opened the car door, the light magically went on. When you closed the door, the light magically knew to turn off. The Mercedes-Benz C-Class has 14 interior lights (including the lower door panel "puddle" lights) to illuminate your way. But with this galaxy of lights comes the increased chance of something going wrong. This article will offer some tips on how to diagnose and fix your interior lighting problems. Major suspects for interior light problems include:

  • Doors not fully shut
  • Burned out bulbs
  • Faulty closing door/hatch contact switches
  • Blown fuses
  • Bad actuator micro switch

Materials Needed

  • Flat head screw driver
  • Phillips head screw driver
  • Needle nose pliers
  • Torx 30 screwdriver

Step 1 Are the doors and/or trunk fully closed?

The interior of the C-Class is quite air-tight. Closing a door with the windows up briefly increases the air pressure inside the cabin, creating a slight resistance against the closing door. You indicator light will alert you to this. This should be the first thing you check.

Figure 1. Make sure the doors are tightly closed.

Step 2 – Check for burned-out bulbs

  • Turn on the interior lighting.
  • If a light doesn't come on, it may simply be burned-out.
  • The light cover can be easily popped off using a small flat head screwdriver or stiff putty knife. Cover the tool with a microfiber cloth to avoid scratches.
  • Wiggle the bad light out and push the new one in.
  • Replace the cover.
Figure 2. New bulb installation.

Pro Tip

Many W204 owners are replacing their OEM factory bulbs with LED bulbs. LED bulbs pull less energy, last longer, and are available in a number of colors. Of course, an LED bulb will cost a little more. Halogen about $1/bulb, LED about $2 to $15/bulb.

Step 3 – Are there faulty door/hatch closing switches?

When you close the door or trunk lid, a button in the jamb is pushed in, telling the lights they can start shutting down. When it is allowed to pop up, the lights are told to turn on. If the switch is faulty, the signal controlling the lights is cut.

  • Visually inspect the switches for corrosion or damage.
  • Pop the switch out and inspect it again for corrosion or loose wires.
  • Use a voltmeter to check that current is passing through the switch. If it is faulty, replace it.
  • A new switch is about $5.
Figure 3. Door light activator.

Step 4 – Check for blown fuses

  • Open the fuse box located on the driver's side of the dash where it meets the door. Pop the door open.
  • The lights are connected through a 15 amp fuse (blue). It is located in in Position PDM. It will say "15" on its top.
  • Use needle nose pliers to pull it out. Inspect it to see if the wire inside it is broken and scorched. If so, you need a new fuse.
Figure 4. Open fuse box.

Pro Tip

Always be sure to replace a fuse with the SAME amperage as the one that had blown. To do otherwise courts disaster.

Step 5 – Is there a bad door actuator micro switch?

If the above steps don't help, you may have a faulty door lock actuator micro switch. A bad switch doesn't give the lights the proper information as to whether the door locks are open or closed. This can cause the lights to stay on, or not turn on at all. Replacing the actuator micro switch takes some time and elbow grease. The door panel has to be removed to access the switch. The switch needs to be released from the door lock mechanisms. A new switch is about $100. Having one installed professionally will cost about $200.

Figure 5. Door lock actuator in the door panel.

Related Discussions