I have a 2009 GL 550. I know the mirrors changed over the years.
About a week ago I started getting intermittent errors that the driver's side led turn signal was not working. I found it hard to believe that the led itself was broken. I took apart the mirror and found what may be a very common problem.
Behind the mirror is a group of about 10 black wires. Obviously they are for the led, mirror adjustment, folding, heat. As soon as I started touching the wires, 2 immediately broke where they were folded. I could see that the wire had some green color indicating that it was already on the way to breaking. Those were not even the led wires. After looking further, I found the led wire that was broken. I stripped and soldered all the broken wires and everything works fine.
If you are having problems with any part of the mirror, I would bet this is the problem.
To remove the mirror, just push is so it is facing all the way down, and pull it out from the top. It snaps right out.
I then took the outside ring off (2009 is a two piece mirror) just to make it easier to get to the wires, but it is not absolutely necessary. There are 4 clips for the outside ring.
Here are some pictures.

 

I am getting an intermittent issue where the right side blinkers go 2x faster than normal. I am betting it is this, going to go try it out right now.

Thanks!

 

Thanks for the info. Repair shop wanted to change the LED light.

 

Thank you for this post and description.

My 09 GL320 had a problem with driver side showing this symptom first. Recently, when we were below freezing temps, my passenger side snapped when unlocking the car. It made a loud enough noise to hear and then the warning light started.

I had the fold upon lock option enabled, which I will now be disabling.

I did not need to remove the front bezel to find and fix the problem.

I used needle nose to hold the wire for stripping (18 guage). I then used needle nose vice grips to hold the two wires together for solder/liquid tape.

Both wires failed at the end of the cloth tape that the factory technician had wrapped the wires with during installation. I have unwound that tape an inch or so on each side to allow the wires to float more, which is probably what the designers intended. If you are going to fold your mirrors and you do NOT have this problem, you likely will. You may want to pop your mirror glass off and see if the tape extends to a point where the wires bend sharply like in my pictures. I would loosen that cloth tape. It really only needs to protect the very back of the wires.

I soldered the wires with the wires pointing the same direction since that takes the stress off the joint. The wires going to the blinker LEDs have to double back. The other wires I noticed with wear marks go to the mirror glass.

The shop's first try was to replace the LED. $127 for the part. Failed. They then wanted to replace the harness...$650 each side plus labor. The shop offered to try to find the problem and fix with wiring repair at the straight shop rate of $150/hr. If you don't know how to solder and have this problem, you can validate your problem by popping off your mirror and then confidently ask them to repair the wires. A stereo installer could even fix this one.

 

When you said removing the mirror, did you mean the entire mirror housing, not just the mirror alone, right? If there are 4 clips, do we need to pry them off? What is the middle round piece? I see it's attached to the mirror, then how can we detach it.

Greatly appreciate it if you can please provide a little bit more details how to remove the mirror.

I accidentally broke the mirror when trying to fix the flasher. Can I just replace the mirror alone?

Thanks.

 

OP -

Couple things - first and obvious....THANK YOU! Just fixed the same exact issue w/ my drivers side mirror.

Couple notes:
1) I checked the passenger side - no issues - the harness was longer than on the drivers side. Interesting that everyone on this thread had the same issue, always on the drivers side.

2) I removed the front trim (4 clips) after the mirror removal and then the entire LED/housing (again - i think 4 clips) - made accessing the wires which controlled both the turn signal/puddle lights very easy. In my case, i had 2 broken wires and 2 which broke when i moved the wires slightly. There are 4 wires there which look like the ones that are prone to break. Its aggravating that all wires are black, was trying to figure out which wire went where - amazingly, my first guess was correct!

3) I also backed off the cloth tape, split the 4 wires out of the harness to give them some added slack/length, and then re-wrapped the balance of the wires.

4) Once repaired, i cycled the mirror through folding/unfolding before reassembling to make sure the wires traveled/hand enough slack/weren't catching on anything.

All in all, probably saved $300-$500 (knowing what the flippin stealers will charge).

THANKS AGAIN!

Aceman

 

Thank you for this information! I have a 2007 GL450 that had this same issue for about a year now, and today I finally got around to fixing it. Unfortunately, I had bought a new LED light assembly 2 weeks ago before I found this thread this morning.
I'm happy to say that this info also pertains to 2007 GL450. When I removed the mirror I saw the one cut wire (I would have never bothered looking at the wires if not for this thread). Turn light works now after I fixed the wire. Thank you once again for sharing this info!!!

 

Ran in to the same issue with my 2010 GL450 earlier this week on the driver side mirror led and bulb.

Took the led+bulb and plugged it in to the passenger side and confirmed led+bulb were functional.

Pulled the wiring with little force and 3 out of 4 wires came out broken. Stripped each, put an inch of shrink tube on each wire, twisted each and then tested the lights to confirm it was wired correctly. Each wire length was few millimeters short/long as I could tell visually to figure out which black wire went to the right one.

Soldered each wire, used heat gun to shrink tube, retested it and it didn’t work. Pulled the light plug out and replugged it back in and it was disco time!

This thread was helpful so I thought I share my experience too.

Thanks folks

 

Annoying design flaw - about to repair driver side mirror a second time on my 2009 GL550. Last round I had to solder a few wires back together. Remember there's wasn't much slack to work with. Might look into replacing the entire bundle of wires. Anyone have a part # for the wire pack?

 

There probably isn’t one … that is, the harness is not a separately available part.

I know when I corrected this problem on mine, I didn’t repair but rather replaced … the entire motor unit with harness. Plug and play.

Just a mostly irrelevant FYI … I later replaced both complete door mirrors on my 2007 with 2011-12 styling units. It was easily plug and play, but the wiring harness was no longer all black wires, but rather lots of colors.

 

Hi, I'm resurrecting an old thread, but am having major issues with my car's Keyless Go. I previously had the issue with a cut wire for drivers side mirror, which I fixed of course AFTER purchasing an LED Light - (If anyone needs one, i'd be happy to sell at less than dealer cost!).

Now my car no longer recognizes when the drivers door is open so I can't turn the car accessories off without the manual Key. So mechanic noticed that when fiddling with wires on the Mirror assembly, the dome light will flicker on and off leading us to believe there are more problems with the mirror wiring harness.

I haven't spoken with him in great depth, but is it possible the goofy wiring harness on the mirror assembly can tie back into the assembly on the door and cause the wiring for the Door Open/Close Sensor to not work? I'm trying not to stomach a new Mirror Assembly when all i need is the wiring harness, silly that can't be purchased. Looking for one out of a junk yard or e-bay next.

He thinks I might need a Door Control Module as well.