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MY ‘21 Inside Rearview Mirror Underside Ambient Light Not Working?

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Old 10-06-2021, 10:42 AM
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MY ‘21 Inside Rearview Mirror Underside Ambient Light Not Working?

Hi Everyone! I recently took delivery of a fully loaded 2021 C300 in lieu of waiting for an incomplete W206 sometime next year. After a few days with the car I noticed that the ambient light located on the underside of my interior rear view mirror was not working after testing under various lighting conditions:



Shortly there after my COMAND system malfunctioned which required me to take the car in for service and I asked them to check out the light. When I picked up the car this morning my advisor indicated that this is normal for MY ‘21 and said he compared against another vehicle, but I’m skeptical that this is accurate. The loaner car I was provided was a MY ‘20 so not exactly apples apples particularly in light of the current chip shortages, but the loaner did feature the same light which DID activate in low lighting environments:



Just wondering if there are any fellow owners of a MY ‘21 with a similar non-operational light, or alternatively, a light that does work, in which case I’ll push to have addressed next time I need to bring the car in for service.

Many thanks in advance!
Old 10-06-2021, 04:24 PM
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Hmmm, try pressing on the interior light off switch and then open the doors (the switch is an image of a car from the top view with all doors open with the words off) if it doesn't work try pressing the the interior light switch (the switch is an image of a car from the side view and a light bulb is illuminated)
Here is an image to help explain, basically the the row of buttons right above the sos switch:
https://ae01.alicdn.com/kf/Hd4efe1c9...33d1d7db5n.jpg

You may also try pressing the switch that controls each reading lights as well (incase the above doesn't work and there is a software glitch in which turning on and off the reading lights will reset it)
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Old 10-06-2021, 04:29 PM
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Forgot to mention, try covering the light sensor if you are testing it during daytime. Just cover the top middle (where the rain sensors are) of your windshield with a piece of dark coloured paper or something you prefer.
Old 10-06-2021, 04:36 PM
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Thanks @W205C43PFL ! I did try that as well, but the darn light just won’t work—the main reading lights do turn on, however. My experience in my other MB vehicles is that this light typically activates when the headlights are on, but there’s no related switch or button. My car, like all other MY ‘21 non- s classes is also missing lights in the exterior door handles presumably related to chip shortage—perhaps they were able to save a chip by making the light inactive. Just odd that I can clearly see the that the LED is there hanging out doing nothing. Hopefully I’ll have better luck when I eventually have to bring the car in for service A. Thankfully this “problem” is one that I can easily live with!
Old 10-06-2021, 04:46 PM
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Originally Posted by MrMBenz1
Thanks @W205C43PFL ! I did try that as well, but the darn light just won’t work—the main reading lights do turn on, however. My experience in my other MB vehicles is that this light typically activates when the headlights are on, but there’s no related switch or button. My car, like all other MY ‘21 non- s classes is also missing lights in the exterior door handles presumably related to chip shortage—perhaps they were able to save a chip by making the light inactive. Just odd that I can clearly see the that the LED is there hanging out doing nothing. Hopefully I’ll have better luck when I eventually have to bring the car in for service A. Thankfully this “problem” is one that I can easily live with!
Sorry to hear that, yup I too heard about them not including the exterior door handle lights but I believe the main reason is because they fail way to easily (cheap quality LEDs) and given how the door has to be removed just to change the light the labour probably isn't worth it for Mercedes (I have all mines replaced on my 2017. when it turns blue it is about to fail) .

Did you try changing the ambient light settings to see if it resets it (try turning it on and off and try setting the brightness to max and then minimum as well as keep on pressing the reading light switches and interior light switches shown in the picture.

Old 10-06-2021, 04:49 PM
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Originally Posted by W205C43PFL

Did you try changing the ambient light settings to see if it resets it (try turning it on and off and try setting the brightness to max and then minimum as well as keep on pressing the reading light switches and interior light switches shown in the picture.
Hmm, that’s an interesting approach. I’ll give it a whirl and report back, thanks!!
Old 10-06-2021, 04:51 PM
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Originally Posted by MrMBenz1
Hmm, that’s an interesting approach. I’ll give it a whirl and report back, thanks!!
Sounds good, let me know : )
Reason I suggest trying that is because electronics are pretty glitchy at times, for example the auto mirror folding requires resetting from time to time by manually folding in and then out. I don't personally have that folding mirror issue but I heard a lot of people experiencing it, nothing a quick reset won't fix though.
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Old 10-06-2021, 09:49 PM
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@W205C43PFL Well I gave it a shot, but sadly no success. Adding insult to injury, I looked over the service report and much to my surprise, the shop never actually evaluated the light despite being told otherwise. My fault for not confirming before leaving the dealership I’ll give them a call tomorrow and see if this is something that can be looked at while I wait—considering the car is brand new I’d actually like to drive it for a bit! Thanks again for your suggestions!
Old 10-07-2021, 08:36 AM
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Originally Posted by MrMBenz1
@W205C43PFL Well I gave it a shot, but sadly no success. Adding insult to injury, I looked over the service report and much to my surprise, the shop never actually evaluated the light despite being told otherwise. My fault for not confirming before leaving the dealership I’ll give them a call tomorrow and see if this is something that can be looked at while I wait—considering the car is brand new I’d actually like to drive it for a bit! Thanks again for your suggestions!
I see, I am sorry to hear that : (

Hmmm, I see hopefully it is an easy fix : ) I would had done the same as well if I overly trust my dealership. Ever since my local MB dealership dented my passenger side door I started taking pictures and recording a video around the interior and exterior of the vehicle with the dealership in the background with timestamps incase something happen (knock on wood so far nothing happened after that first incident but better safe than sorry, I am hoping nothing similar that I experienced happens to your car and you won't have to deal with anything remotely close to what I experienced) but ever since then, I learned to not fully trust my dealership. That being said, I don't visit a MB dealership anymore as my warranty has already expired.

No problem at all, glad to help! To be honest you are more than reasonable to expect everything to be working as intended and so you can drive it without issues being a new car and especially from a car from a luxury brand. Good luck getting everything sorted : )

Last edited by W205C43PFL; 10-07-2021 at 08:40 AM.
Old 10-11-2021, 10:10 AM
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Originally Posted by MrMBenz1
Hi Everyone! I recently took delivery of a fully loaded 2021 C300 in lieu of waiting for an incomplete W206 sometime next year. After a few days with the car I noticed that the ambient light located on the underside of my interior rear view mirror was not working after testing under various lighting conditions:



Shortly there after my COMAND system malfunctioned which required me to take the car in for service and I asked them to check out the light. When I picked up the car this morning my advisor indicated that this is normal for MY ‘21 and said he compared against another vehicle, but I’m skeptical that this is accurate. The loaner car I was provided was a MY ‘20 so not exactly apples apples particularly in light of the current chip shortages, but the loaner did feature the same light which DID activate in low lighting environments:



Just wondering if there are any fellow owners of a MY ‘21 with a similar non-operational light, or alternatively, a light that does work, in which case I’ll push to have addressed next time I need to bring the car in for service.

Many thanks in advance!



Do you mean the one in red, or the one in blue? I’ve a 2021 C300 as well and I was wondering after seeing your post which one you’re referring to. I didn’t know these lights were supposed to turn on automatically other than when you open any doors.
Old 10-11-2021, 10:20 AM
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Originally Posted by sids2112

Do you mean the one in red, or the one in blue? I’ve a 2021 C300 as well and I was wondering after seeing your post which one you’re referring to. I didn’t know these lights were supposed to turn on automatically other than when you open any doors.
Hi @sids2112 ! The light circled in red should (in my experience) illuminate when opening the doors when all interior lights activate, i.e., welcome lighting which includes both the blue circled light as well as the red. However, the red circled light should also illuminate when operating the vehicle at night or in other low lighting scenarios. In my case, it just never turns on at all. It’s one of those things that you’d probably never notice as it only casts a very faint light over the center console, but since I know the light is there, I would still prefer that it works
Old 10-11-2021, 10:26 AM
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Originally Posted by MrMBenz1
Hi @sids2112 ! The light circled in red should (in my experience) illuminate when opening the doors when all interior lights activate, i.e., welcome lighting which includes both the blue circled light as well as the red. However, the red circled light should also illuminate when operating the vehicle at night or in other low lighting scenarios. In my case, it just never turns on at all. It’s one of those things that you’d probably never notice as it only casts a very faint light over the center console, but since I know the light is there, I would still prefer that it works
@MrMBenz1 Interesting. Learnt something new today. I will check it out after I get my car back from the dealer. It’s in for a wind noise fix.
Old 10-11-2021, 10:31 AM
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Originally Posted by sids2112
@MrMBenz1 Interesting. Learnt something new today. I will check it out after I get my car back from the dealer. It’s in for a wind noise fix.
Ha! Are you hearing wind noise from the from driver’s seat position? I have it too and have been debating whether or not to bring it up to my advisor, but am always a bit skeptical that they won’t come back with the typical “no issues found at this time.” I also have a horrible rattle from the rear deck area which I can 100% duplicate, yet when they checked it out they observed no rattles of course.
Old 10-11-2021, 10:35 AM
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Originally Posted by MrMBenz1
Ha! Are you hearing wind noise from the from driver’s seat position? I have it too and have been debating whether or not to bring it up to my advisor, but am always a bit skeptical that they won’t come back with the typical “no issues found at this time.” I also have a horrible rattle from the rear deck area which I can 100% duplicate, yet when they checked it out they observed no rattles of course.
Driver and passenger side. Went for a test drive with one of the foremen at the dealership and he instantly agreed with me saying it’s bad. He said he’ll look into performing the steps from the wind noise TSB for earlier W205s while consulting with MB if that bulletin still applies and try and get me the acoustic glass if the steps don’t work.
My COMAND interface also died and restarted once last week which is shocking since I’ve only owned the car for a month. They’re looking into that too.

And yeah my previous A Class had a rear rattle that always disappeared when I went on a drive with the dealership guys. It’s annoying.
However, not good that a new C Class has a rattle. ☹️
Old 10-11-2021, 10:39 AM
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Originally Posted by sids2112
Driver and passenger side. Went for a test drive with one of the foremen at the dealership and he instantly agreed with me saying it’s bad. He said he’ll look into performing the steps from the wind noise TSB for earlier W205s while consulting with MB if that bulletin still applies and try and get me the acoustic glass if the steps don’t work.
My COMAND interface also died and restarted once last week which is shocking since I’ve only owned the car for a month. They’re looking into that too.

And yeah my previous A Class had a rear rattle that always disappeared when I went on a drive with the dealership guys. It’s annoying.
However, not good that a new C Class has a rattle. ☹️
Happy to hear your service team is proactive and perhaps I’ll take the plunge myself. Sorry about your COMAND issues—mine (also about a month old) had to be replaced as it would not accept over the air updates. So far things seem to be operating as normal now. The “joys” of Mercedes ownership!
Old 10-11-2021, 06:44 PM
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Originally Posted by MrMBenz1
Ha! Are you hearing wind noise from the from driver’s seat position? I have it too and have been debating whether or not to bring it up to my advisor, but am always a bit skeptical that they won’t come back with the typical “no issues found at this time.” I also have a horrible rattle from the rear deck area which I can 100% duplicate, yet when they checked it out they observed no rattles of course.
I have/had a rear deck rattle as well on my 2020, I couldn’t figure it out and didn’t want to bring it to the dealer until I knew what it was so they couldn’t bs me. Turns out it was my comfort box, I was sitting in the back and was thumping on the rear deck and noticed it seemed to be coming from the trunk, sure enough it went away after I removed my comfort box. I had the same issue in my old E class, but it didn’t cross my mind that it could be the same issue. I leave it in as I only hear it when sitting in the back, but I felt like I was going crazy because no one else could hear it in my family.
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Old 10-11-2021, 08:00 PM
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Originally Posted by 2010C-class
I have/had a rear deck rattle as well on my 2020, I couldn’t figure it out and didn’t want to bring it to the dealer until I knew what it was so they couldn’t bs me. Turns out it was my comfort box, I was sitting in the back and was thumping on the rear deck and noticed it seemed to be coming from the trunk, sure enough it went away after I removed my comfort box. I had the same issue in my old E class, but it didn’t cross my mind that it could be the same issue. I leave it in as I only hear it when sitting in the back, but I felt like I was going crazy because no one else could hear it in my family.
Thank you @2010C-class! I completely forgot about that—I have an old one that I put odds and ends in in my trunk which thankfully doesn’t make noise once in box shape. Taking the one from under the trunk mat out right now. Have an early drive in the morning and will report back. Thanks again!!!
Old 10-11-2021, 10:05 PM
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Originally Posted by MrMBenz1
Thank you @2010C-class! I completely forgot about that—I have an old one that I put odds and ends in in my trunk which thankfully doesn’t make noise once in box shape. Taking the one from under the trunk mat out right now. Have an early drive in the morning and will report back. Thanks again!!!
Let’s hope it’s as easy as that! Glad I could help!
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Old 10-13-2021, 03:51 PM
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Old 11-14-2023, 01:39 AM
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Did you have any updates about that issue? Did it solve? I have the exact same problem on the 2022 W213 FL the ambient light on the mirror doesn’t illuminate at all no matter what setting of light I choose either from mbux or the physical buttons (check at night and day)

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