CLS LED Multibeam Headlamp unit problem/fault

[vinnykoo]

Hello! new to the forum and relatively new to mercedes ownership. Thought this might be the place to ask questions and get help of this sort.

UK based, Bought a 2016 CLS 350D Shooting Brake about 5/6 months ago and has been a pleasure and faultless to drive... until, about a few months ago when an intermittent fault developed with the driver side headlamp. I have the multibeam LED headlamps that (im fairly sure?) were standard on all mercedes cls sold in the UK of this year(s). Because it's the headlamp, the fault is only really noticable at night and pretty sure that this doesnt occur during the day/when the lamps are not in use.

Every so often when driving there is noticable dip in the amount of light being thrown on the road from the drivers side, doesn't go full on dark on that side but a drop in about 20%-30% of the amount of light being thrown, this used to happen once every 3/4 drives, now its nearly everytime the car is out at night. Ive noticed that something is up with one of the smaller units in the main unit after seeing something dip/switch off/on in the reflection of the a car in front at night, but admittidley was very hard to be 100% sure. The fault is definitely just secluded to one side, not both headlaps, as kerb side has no change in the amount of light or throw. The dip lasts for anywhere between 2-6 seconds, and can occur anywhere from 0-8 times an hour on a drive.

Intrestingly - this fault seems to appear most of time (but not secluded to) happening under acceleration. Not hard accelrating just moving off is enough and like I said before its not just here it happens, the light can dip just doing a steady 70mph - could this be a power problem?

The auto headlamps feature - auto switch on/off and auto switch high beam/oncoming traffic all apprears to be working as it should as does all the other parts of the unit - daytime running light and indicator all working fine.

Ive attached a pic below on the headlamp in question, unfortunately I havent been able to get a video of fault as its almost impossible to guess when this is going to happen and also to film the headlamp while moving. Ive a suspicion that the A unit (cornering lamps?) is the offender here as the there is still enough main light on the drivers side when the dip occurs. I'm also assuming the lamp unit not highlighted in the picture is the full beam lamp.

Thanks for reading and your time, any help sheding some light ( - no pun intended), or if anyone else had heard or come across this problem would be very much appreciated.

 

[mioba]

could be the PO got some aftermarket replacements in there, have a look at the backs of both to determine if genuine or not.

 

[dry run]

Welcome to the forum I have the Coupe version of that car with the same headlights. The lights definitely are different to previous Mercs I've had and do "switch around" due to oncoming traffic or when following cars. Maybe it's doing what it should??

You could check that the sesors in the windscreen are clean. Other than that find a good Indie in your area.

 

[vinnykoo]

Thanks for your reply guys, appreciate the time.

Forgive my ignorance, but PO?

I don’t think it’s got anything to do with the windscreen sensors as this is different to using ‘full beam’ this is only occurring when NOT using full beam, so normal condition driving at night. The dip in light occurs from standard lamps at night driving, not with full beam, I assume it does do it when using the full beam are so much more powerful that it would be impossible to see from in the car.

It feels more like the ‘A’ units in the picture below are the lights at fault here.

And it’s not a 100% loss of light from one side of the car, just a small dip, but noticeable enough, happens when not in motion and when there also no cars around - I assume the normal night lights DON’T dip and only the full beams are.

 

[dry run]

PO = Previous owner.

 

[dry run]

When your headlights come on do they start by sweeping out and then back in before leveling up? Seems to me that is a check the car does to establish that all the LEDs are functioning correctly. A video from outside the car would be useful - although difficult to achieve. Good luck and please let us know what it was when you eventually get it fixed.

 

[mioba]

Could also be failing LED unit, the solders do dry out leading to poor conductivity.

 

[vinnykoo]

Hey all, thanks for the help. Yeah they do sweep and then level up, every time. All parts from factory.

Guess that would be an entire replacement headlamp? Ugh..

 

[s5tuart]

I would try to rig up a test with the car running but stationary.
You can certainly test the cornering lights at a standstill.
Then stand in front of the car with a powerful torch aimed at the windscreen sensors and see what happens.
If it does the self check then I doubt (hope) there's not a lot wrong with it and possibly working as designed.