I've tried to search this everywhere - maybe I missed it but no luck at all.

2014 ML350 4Matic, Bi-Xenon headline package (Code 615+840)

Got a warning - "Check Left Low Beam". Lamp was on but dim. Then it started to flicker. This AM that lamp was dark except for the amber LED strip that runs across the top edge and the warning was "Active Assist inoperative".

Has anyone dealt with this? Are the control units accessible? There are two - which would be the one that addresses this issue. Can this be a bulb issue? My thinking is that it is not - but I'm in the dark on this.

I only have experience with basic HID: power source, ballast, HID bulb. when the bulbs fail, they tend to do so progressively, changing color in the process. What you've described lead me to think the ballast is failing. A test of this would simply be to swap the left with the right ballast. If the dimming effect follows the swap, the answer is bad ballast.

__________________
-- raymond~
47º 34'N 122º 18'W

Thanks Raymond. Your experience mirrors mine. The issue I have is there are 2 "controllers" on each headlight. The parts system description doesn't define them clearly enough to know which is the ballast. Anyway, since my spouse is in the hospital I don't have a lot of time on my hands to resolve this. It is going to the dealer next week. They treat me well there (even though I do most on my own work) so I'm willing to trust them with this.

Swap the bulbs and see if the problem moves........

[QUOTE]Swap the bulbs and see if the problem moves......../QUOTE]

Yes, I know that trick. I resisted trying that because I knew it would be difficult based on my previous explorations back when we bought the car new. But, valuing your knowledge I forged ahead.

This falls into the category of "easier said than done". Access to the back of the headlight is through a convenient access hatch in the front fender liner. Access to the bulb is through a round cap, easily removed. The photo shows what I believe to be the actual ballast - sort of like "coil on plug ignition" I believe the ballast is connected to the back of the bulb. First problem is the connector. Access looks fairly easy in the photo due to the angle of the camera. The connector is actually just below the rim of the access hole. It took a few minutes to figure out how the detach it. I did so knowing I might be in a world of hurt later trying to re-attach it.

At that point I tried to remove the ballast but could not figure out how to do do. I finally gave up and spent 30 minutes fiddling with the connector, trying to line it up with the socket and press it upward into place.

All totaled I spent 1 1/2 hours getting nowhere, As I stated above I looked the car over for things like this when I bought it in 2013. This is one job that looked like it was going to be very tough - and it is.

I'll let the dealer deal with this. I don't need this on my plate right now.

Attached Thumbnails

 

I tried to swap the bulbs again. I have been working on the left unit because that is the one that is out. After checking my WIS again I decided to apply more force (a lot more) to the ignitor/bulb unit. It finally came out as described in the WIS. The right side came out easily. I did the swap and it shows that the bulb is faulty.

Thanks for the replies.

thank you for updating the thread with your results. good learning op. can
you clarify if your car is using a D1S bulb (which has additional module
attached to the base), vs the older D2R and D2S bulbs

__________________
-- raymond~
47º 34'N 122º 18'W

D1S.