A small tidbit on this issue.

MB UK are equally ADAMANT that they are going to do NOTHING about this problem.

Following extended correspondence with them they eventually agreed my technical analysis was correct BUT stated that since the car was only covered by 3 year warranty (only introduced a month or two previous when it was only 1 year) any failure outside this period was not their responsibility, even though it is safety related.
The legal system operates very differently in the UK.

The bulb wattage issue is a smoke screen. Part correct / Part incorrect.

UK, and othere territories have different bulbs and bulb holders for the brake lights than does USA. The USA (SAE/DOT) vs European (EII) bulbs do have a slightly different wattage with the SAE bulb having the slightly higher wattage. This difference is identified by different coloured bulb holders (for factory identification purposes). From memory the SAE holders are pink. UK black or grey.

HOWEVER UK cars also suffer from the same intermittent operation issue due to deformation of the light cluster moulding. Key parameters appear to be Automatic vs Manual/Stick shift gearbox and traffic driving. (Extended use of stop light whilst stationary which is much more prevalent in the UK than many parts of the world)

I cannot be 100% sure whether the initiating fault is 1 or 2 below since I do not have the stats.

1. The temperature generated by the (poor) contact between the bulb holder and the galvanised strips on the lighting module
or
2. the heat generated by the bulb.

I personally believe that the problem is due to heat generated at the bulb holder to cluster/module interface (which may be made worse by the slightly higher current flow) caused and SPECIFICALLY by the bulb holder being a tight fit in the cluster moulding and thus reducing the contact pressure of the connector.

Certainly once the problem manifests itself the holder is a tight fit because the main cluster moulding has "melted" (softened) in the area and inadequate clearance then exists between the bulb holder and the main housing.

I resolved my problem by enlarging the hole in the cluster housing (to give clearance) and cleaned / soldered (tinned) the contact surface area on the galvanised conductor strips to overcome the pitting (sparking corrosion) issue in the area of the contact.
In addition a new bulb holder was fitted since the moulding had melted locally due to excess heat from the poor contact. Voila! 40k miles and not a hint of the problem returning.

In my view this is a parts Quality issue rather than a fundamental Engineering shortcoming.
After all MB use similar design on many other classes of vehicle which use similar designs (and manufacturer) but do not exhibit the same issue.

Stuart

 

I posted my opinion on this issue yesterday, but so far can't find it and think MB Forum watchdog may have deleted it because of hitting too close to truth.

Tailight moulding is a mistake and only works for a few years by luck.

There is an excessive gap created by design of brakelightchassis and standard globe holder.

Brakelights are failing (flashing) causing pitting long before fail completely.

Is a complete defect which has no excuse. While the globe holder springelectrical contactis fresh and no pitting on tail-light chassis by electrical DC arcing globe will work. After a couple of years then you need to start fixing yourself or fork out $$$$.

It needs a 1.5 to 2 mm spacer on galvanised electrical brake light chassis electrical contact strip. Doing mine tomorrow on passenger side. On mine think driver's side not as bad. At least not yet. I have a degree and trade in mechanical engineering an designis a 1 out of 10.

 

Hi,

I saw your post yesterday.

However I'm not totally in agreement with your analysis of the defect. Don't forget that the design is basically common for all the bulb holders and is also common to most MB models...and other vehicle manufacturers who use this design principle (majority).

So where do you believe a spacer is required? What is the purpose of the spacer?
IMHO the reason for the poor contact is due to the heat generated through the bulb holder to cluster strip connection due to inadequate contact tension which in turn is due to poor dimensional tolerancing on the holder to cluster interface.

Enlarging the hole in the cluster (so that the bulb holder can "float" and find a comfortable position for the electrical contacts to apply their full force to the galvanised cluster electrical strips) + repair to the pitted surface on the electrical strips + a new bulb holder is in my view all that is required. Bazzles solution totally eliminates this "removable" electrical connection.

I suspect that excess temp is generated between the holder and cluster conducting strips not only due to the lack of spring contact force (bulb holder doesn't seat correctly) but also due to the (high) current through such a poor material interface. Tinned copper/brass onto galvanised steel especially since the galvanised surface tends to corrode with moisture over time.

Stuart

 

Thanks for Heads Up Bazzle, I suspected we're on our own and yes I'm in Oz. I'll tackle the brake-light tomorrow before heading off on my road trip up north.One of the good things about a sports convertible is that there are are always plenty of 4 x 4 drivers casually looking downat you to advise you that your lights are out. :-).

Naturally I'm currently praising MB at the moment.

 

Thanks for reply post,

I am taking the tail light assembly out tomorrow and will get my first unobscuredlook at the assembly in full. As far asmy assembly goes, when I reviewed the brake-light asbest I could in full daylight before going to work, it appeared to be the same as my initial assessment. In a previous jobmy role was to do detective work on biomedical equipment faults in the US from an Australian based manufacturer without leaving Australia, so for the present I am still backing myself. However, I could be about to make a clown of myself ifI pull this tail-light assembly out tomorrow and I have it wrong.

I'll definitely take a photo, which it looks like I can post. Hopefully,for my slk230 at least the photowill show that this is the problem my model has.

 

Well that didn't take long.

Lesson learnt. I'm still able to make a goose of my self by jumping to conclusions on an incomplete examination. I just ran out and pulled the light out, and yes from the angle I was looking at it still looked exactly as I had observed, but from inside the globe holder hole the deformationfrom heat can now be clearly seen.

It's only melted on one side which is a little surprising.

Signed: Not going to be so ready to jump to conclusions next time, but now still need to fix the damn thing.

Cheers.

 

I used to do Engineering warranty investigation for Land Rover / Jaguar amongst other companies in the group.
Send us your email by PM and I will send you detailed photos of the problem.
For reasons I have not yet got to the bottom of this site won't allow me to post correctly sized photos. Think the problem is related to the fact that I use a MAC and the suffix is not automatically added to jpg files when i try to upload from my directory (iPhoto)

Stuart.

 

Some pix

Bazzle


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