W204 lighting problems

[NDFR]

Hello I could do with a little help...

I am getting error messages for

Rear left turn signal
Rear left brake/tail light

continuity check of all bulbs show they are fine and the connections in the bulb holder are also OK.

Switching off and restarting the car clears the errors for a short time then they will reappear. I am assuming it's going to be the rear sam module at the moment.

I would welcome any other suggestions though, in addition can anyone suggest someone for repair of the module rather than replacing?

Thanks.

edited to add: If driving without braking (motorway for instance) the turn signal error is not triggered when indicating, indicators will work normally. Once the rear brake/tail light error is triggered, the turn signal error will appear on the first use of indicators. Hopefully that makes sense.

 

[XJ600]

Would suggest checking ground connections first.

 

[Ted]

What XJ600 says.
Check to see if the brown wire is melted where it plugs into the light unit.
There are repair kits available or you can do it yourself.

 

[PaulPJ]

I started a thread just last week about this as the Brown wire and the plug had melted in the NSR light Unit of my C180K. It appears to be a known fault. I am interested in the repair kits available as I asked about repairing but didn't get much response. Paul

 

[Ted]

Mercedes-Benz C-Class Right LH N/S Rear Lamp Loom Repair Kit Bulb Holder Plug | eBay

Recalled in the US
Tail Light recall is now active - Mercedes-Benz Forum

 

[NDFR]

I can give an update on this, thanks for your suggestions guys/gals.

I had noticed some discolouration in the bulb carrier and had ordered one from Mercedes Newcastle for under £20, which arrived today in the post. I've used them several times recently and they impress me a lot, they answer emails very quickly and ship the same day too. Anyway...

Having now fitted the bulb carrier lights are now working normally 'touch wood'. The connector has signs of overheating too so I'll need to replace that as soon as possible but for now it seems I'm OK.

Thanks again for chipping in with suggestions I appreciate it.

 

[PaulPJ]

Glad to hear you have sorted it. Mine is sorted after a fashion now. I have bypassed the connector with 2 of the wires, (brown being one of them) and soldered the wires directly onto the bulb holder. I will see how this goes before ordering a new bulb holder and connector.

 

[NDFR]

Glad to hear you have sorted it. Mine is sorted after a fashion now. I have bypassed the connector with 2 of the wires, (brown being one of them) and soldered the wires directly onto the bulb holder. I will see how this goes before ordering a new bulb holder and connector.

My problem is with the brown wire too actually.

 

[Ted]

That is because the brown wire carries all of the current (as the return path) of the other wires.
Si if you have the side lights on (1/2 amp) and your foot on the brake (2 amps) while you are in reverse (2 amps) the brown wire will be passing 4 1/2 amps.
(all above figures are approximate )

 

[XJ600]

Would still advise checking the ground connection(s). The cause of the overheating can be caused by a poor ground connection.
If you have a voltmeter, test voltage across neg terminal at battery and the ground point to be tested.
With the lights on.
Anything >0.2v max would indicate a poor ground, remove and clean ground and recheck.

 

[Coops71]

Would still advise checking the ground connection(s). The cause of the overheating can be caused by a poor ground connection.
If you have a voltmeter, test voltage across neg terminal at battery and the ground point to be tested.
With the lights on.
Anything >0.2v max would indicate a poor ground, remove and clean ground and recheck.

I had this issue with a C Class some years ago. The Earth on the bulb holder fitting is the issue and a poor design. Once I upgraded the Earthing which was a simple fix if you have a soldering iron and the problem was resolved. I have done the same fix for other family members since with the same result. I contacted Mercedes in regards to this failure and they responded with they hadn't come across this issue previously. Comedians

 

[ALFAitalia]

He may have fixed it in 5 and a half years since he posted the question!

 

[Coops71]

He may have fixed it in 5 and a half years since he posted the question!

That is absolutely correct. BUT If I feel I have factual information that I can share that could help just one other person in the future on this site with the same electrical issues then I haven’t wasted my time or anyone else’s

 

[ALFAitalia]

That told me......