Left Headlight Stays On After Locking - 2017 E-Class Estate

[Oobals]

I'm looking for some advice regarding an issue with my 2017 Mercedes E-Class 220 Estate. When I lock the car, all the lights initially turn off as expected. However, after about a minute, the left-side dipped headlight comes back on and stays on. This happens regardless of whether the lights are set to auto or manual, and there are no fault warnings. I've tried adjusting the indicator stalk in case it was related, but the problem persists. Does anyone have any ideas on what might be causing this?

 

[eng.aws]

Do you have dynamic or static headlights? If they are static headlights, then most likely the problem is in the headlight control unit.
If they are dynamic headlights, then there can be many reasons, some of them are incorrect PXL ECU coding or damage...

 

[Oobals]

Thank you for your reply. I believe the headlights are static, but I'm not entirely sure. Last night, I turned on the left parking light and locked the car, but the left dipped headlight didn't come on. Do you know where the headlight controller is located? Is there one on each side?

I also tried downloading a workshop manual from Easymanual, but could load they did send me a PDF document, but it wasn't helpful. Could you recommend a good workshop manual or let me know where I can find a wiring diagram for the headlights and related modules?

 

[liverepair]

Common problem with water damage to front SAM or left headlight LED driver problem.

 

[Oobals]

Do you have any ideas how I can prove the problem is with the SAM or the LED driver, or information on these types of faults?

 

[liverepair]

Yes, first I would take everything apart and check for water marks or damage on the connectors, headlight and SAM unit inside, water usually causes the most common defects.
Also, as far as I remember, the connectors for the left and right headlamps are the same, so I would swap the headlamps to test and see what happens.

 

[karakan08]

99% - LED controller damaged (water), also check front SAM for oxidation.
Had exactly the same problem with a W213 where one headlight would randomly turn on when the car was locked. As a result, we had to replace the headlamp and the control unit (at first we changed the control unit, but after a few months everything started again).

 

[Oobals]

Thanks to liverepair and karakan08 for useful tips. Around the time the problem started, I noticed condensation in the left headlight. Is the headlight particularly sensitive to water ingress? If so, where should I look for potential problems when I remove it?

I am planning to order a new LED controller which I believe is Mercedes part number: A2139005711. Should I consider purchasing aftermarket parts and is this module ready to use?

When you mention checking the SAM for oxidation and water damage, are you referring to the SAM located in the fuse box connector at the rear of the engine bay, or are you talking about the LED controller?

 

[nabs84]

Hi, this might be a stupid question, but isn't that the left side marker light?

 

[bigchevy66]

Replace the headlight assembly and the headlight control units that are attached to it. Yes, the control units must be coded for the vehicle and headlamp.

Water getting into a headlight is usually the result of damage, but I have seen headlights with factory defects.By the way, Mercedes actually had a special adapter that plugged into the electrical connector of the headlight, and you could force air into the headlight with a hand pump, and then check for bubbles with soapy water. It was quite an interesting tool. In any case, if there is water in the headlamp, it is better to replace it.

I can't comment on the aftermarket parts, since I have only used factory parts for those headlamps.