uchu47

Got a faulty rear light message yesterday. After checking the block all the bulbs were ok, but ground(?) wire completely rusty and half melted, causing intermittent contact.
Managed to carefully clean and press contacts together and it works (for how long it remains to be seen).

After reading a while about it, it seems like a very common issue for W204. In some countries it was considered a recall. Opened my other rear block - the ground wire is in same condition.

Whats the best way to deal with it? I have ordered new plugs with a proper thickness wire so thinking replacing original ground wire all the way (if it is doable without dismantling half of car - not sure how long it is) or at least the part coming into the plug, while soldering it to debris of old original ground wire.

TimC300

What year W204?

Im not sure what the "block" is, and you write that the ground wire is completely rusty and half melted. The entire wire? photos would be helpful.

I would just remove and replace the damaged parts. if its just a rusted connector inside the harness then remove that connector and crime on a new one and put it back in the harness. if you need to remove some wire just cut it and add some new wire so its the right length again. I like to solder all my wires then cover with heat shrink

Below is for 08-11.

uchu47

thank you. My W204 is 2009. Sorry for not including a photo - didn't make it on the spot but below is online photo, mine was exactly same, slightly worse condition.




4 bucks per pin is a rip-off but no seems like no choice. Will ask local dealer with part numbers - thank you

TimC300

Hopefully you dont need a new carrier, but if you do they are only around $22 and come with new bulbs so thats a plus.

The connector at the Mercedes dealer near me is $4.20 each. Or search online for "Molex Female Connector" and see if you can find the right size, I dont know the specific size so not any help. Or ebay has a few options.

TimC300

I forgot to mention you should check to see if any water is getting in your trunk that caused this issue. I recently resolved water getting in my trunk by replacing the rubber-type fasteners that hold the trim on.

Here's the post I made about it with photos and part #'s. https://mbworld.org/forums/c-class-w...ar-window.html

uchu47

thanks a lot @TimC300 ! It seems to be purely related to electric as only ground cable is destroyed. all other ones are in good condition. Will either replace whole set or go as some youtube video suggest by soldering proper wire to ground on light cluster and putting it to ground pin next to fuse block.

Just204

I just had this a couple weeks ago. You will need a new bulb carrier( didn’t come with bulbs), new connector, and what we carr a pigtail to replace the wire(that’s the killer, dealer charged $17 for it but I had to, a police ticket would be a lot more). Supposedly the ground wire isn’t fully sufficient for the tail light, so it gets overheated and melts. Mine has lasted 11yrs so I’m not too scared about it but you can also solder a new ground off the carrier. A number of people use a heavier gauge and they say that it’s a Permenant fix. Being an ex dealer tech I prefer the official repair only, but may make a second ground. This is not from water damage so don’t worry.