Four problems related to trunk wiring have been reported for the 2009 Mercedes Benz C300. The most recently reported issues are listed below.
I received a warning on my dashboard that my right rear tail light, right turn signal and back light needed to be checked and malfunctioning. The message came and went for several days. When I opened the compartment where the tail bulb carriers and assembly were, I saw that some of the lights were very dim. The carrier itself was piping hot. So my first reaction was to replace the bulbs. I did. Same problems, nothing was fixed. The next day, everything cleared up. . . So I thought it might be fine. A week later, it came back. When I opened up the compartment again, it was super hot, and I noticed that the wiring was browning and it burnt my finger. I immediately stopped driving the car. I went to the dealership and they said it will cost hundreds to replace and not covered.
Right rear tail light was dim; strong smell of burning wiring in the trunk, wiring harness was hot to the touch, at least one wire on the harness was charred / burned. Dash warning light eventually came on. Brought to m-b dealer; not covered by any factory warranty, recall or the 3rd party extended warranty.
On 8/8/2013 my information display indicated my right taillight, blinker and brake lights were out. When I opened the compartment to see what type of bulbs to replace I found the problem to be much bigger than expected. The plastic housing that hold the wiring pin, the wiring pin and the brown ground wire were all burnt up causing the lights to fail. I than opened the left tail light compartment and the same thing is happening, there is already signs of the housing burning. I remember smelling something burning in the car a few weeks ago. I now know what it was. I am surprised it did not catch fire. I contacted mercedes service only to find I am responsible paying to have this issue corrected. I only hope the left side does not cause a fire before I am able to get it fixed. This is clearly an unsafe electrical issue.
The information system in my car gave me the symbols for the right back lights. I stopped to check and realized my lights were out. I opened the wiring in the trunk and realized that the brown wire on the outer side burned through the connector and the lamp carrier.