W204 rear light cluster / numberplate light niggles....

[cfoster]

I thought I would post my findings / resolution and ongoing issues on a rear light cluster fault I have been getting / starting to happen on both of my C Class' (W204).

One of the W204's is a 2008 C220 cdi sport, for ages now the rear left hand light cluster looked slightly dimmer than the right, it then kept intermittently flagging on the dash that my left rear side light was faulty, then the rear left number plate light etc. It got worse and eventually it was telling me every time I got in it, then the rear left indicator was flashing fast etc etc...

I pulled the bulb cluster out and noticed that the earth wire that goes into the clip was very black and burnt looking, it had melted the edge of the plug around the earth wire. I was quite sure this was the issue (bringing back memories of XR2's / RS Turbo / Cosworth days of dodgy earthing!). The clip was so burnt I managed to breakaway all of the wire and metal prong thing and remove it. I've bypassed the plug by routing a new earth wire around the side and soldering it to the existing earth loom. Hey presto, all lights are perfect and not dim / no errors on dash!

However, the number plate one still intermittently tells me its out. If I bang the tailgate it comes back on?!! I've got to the back of the number plate bulb and the fitting is secure and all wires are good, any ideas?! I've swapped the left / right bulb around but still same side has issues!

At the same time I thought I would check my C63 (2010) wiring, guess what, the plug has started to burn away as well although no where near as bad! I have currently clean all the crap of the plug so will keep an eye......

Having googled it it seems a common problem and was a recall going back (it can set alight - apparantly....).

 

[optimusprime]

Thats good information worth keeping in it mind.Nice of you to post it on the forum

 

[ash59fifty-uk]

This is notorious on the MBworld forum

On a slightly different note I changed to aftermarket number plate lights from autobulbs which thrown a rear right numberplate lamp error after a month, banging on the boot would bring it back on

Bought a different set from Amazon which are a million times better, and (touch wood) are still perfect after three months

 

[190]

It is an inherent fault and there is a recall in the US for it because they kicked up a fuss on safety grounds but I don't know about anywhere else. As I understand it even if you don't have the problem it's a good idea to fit a supplemental earth wire as a preventative measure.

Presumably the current draw of the rear lights and brake lights together is too much for the size of the earth connection. I've been meaning to inspect mine and fit the extra earth wire. In the mean time I've been careful not to have the brake lights on for extended periods when stopped.

This is very basic design flaw and it's shameful that MB didn't get it right.

 

[cfoster]

190 - you are indeed correct, i'm no electrician by any means but having around 8/9 bulbs at say 15w minimum each that could potentially be on at once probably draws too much current / heat for the single small earth wire coming from the plug. The wire itself seems ok its the plastic connector that seems to have suffered. Hopefully bypassing it has solved the problem.

With the numberplate lights i'll replace with new ones and see how I go!