Parfumeur

>> Indeed, the brown wire as well... MB most probably made an error in selecting a wire which is not flexible enough.. <<

The issue is not the flexibility, but bad electrical engineering. The brown wire is a common ground, and if power from multiple sources returns through this wire, it will melt the insulation, and stiffen the copper, so that when flexing it will break. If you look carefully, you will see that it overheated and the insulation is melted. Copper will lose it's flexibility when heated and cooled multiple times, and that is the weakest point.

NOW, MB had the VERY SAME issue with previous model in the die cut metal wiring in the tail light assembly. The metal heated and melted the plastic tabs holding the die cut, loosening the bulbs, and losing contact.

Personally, this is not acceptable for MB. There must be an incompetent electrical engineering in the tailight wiring section. He does not take into consideration long wait times with the foot brake on, drawing too much current and burning out the return ground. The ground should be of a thicker gauge. When stuck in traffic, better to put the car in neutral, and off the foot brake. Think of your toater, and how the wires get hot..... here the return ground from multiple stop light overheats.

N_Jay

I saw no signs of melted insulation on mine. There may have bene some hardening of the last few strands from heat, but I am fairly sure that coccus are most of the wire had already broken from flexing.

Get in the trunk (or put a camera in the trunk) and look at the amount of bending during the last few inches of trunk closing.

Beav

Great thread, thanks to all those who contributed!
My issue is a little different. 03 E500, automatic trunk closer does not function. The trunk will open an inch then I have to force it open, to close I have to force it close until it strikes the locking latch and that motor pulls it closed and locks. The high mount brake light, license plate lights, interior trunk lights and red trunk close button are all working. I examined wiring and found that the wires had been repaired once before and examined the repairs under the electrical tape and everything looks fine. When I press the trunk close button I hear a click sound from the electronic module by the gears but no sound from that motor attached to the gears. Could I have a bad motor? I keep going back to the wires trying to find a flaw in one of the wires but can't find anything that hasn't already been dealt with. Does anyone have any suggestions? Thank you!!!

N_Jay

Bad motor, bad sensor on the gear, bad controller, or one or more of the switches in the upper or lower latch part is bad.

OR . . . .

You can do like me, and test every part you can, (all but the controller), then decide it had to be the controller and buy one off ebay, then put it all back together and have it still not work, then swap the old controller in and all of a sudden it starts working.
Anyone want a spare controller module?

Beav

Does anyone happen to have a diagram which identifies all of these related parts that N_Jay mentioned?
Also, does anyone have a diagram of what each of the wires in the harness controls?
Thanks!

N_Jay

See if this helps

Beav

Thanks N_Jay
I took a second look at all of the wiring and aside from the fact that some of the wire sheaths are frayed the copper is still strong and connected so I can be reasonably certain it is not the harness. When I press the red illuminated close button I hear a click from near the motor which I assume is that electronic module trying to communicate with the motor but of course no response from the motor. Does it make sense to assume that it must be the motor assembly that is at fault (2118202042)? Is there any way to test the motor specifically prior to removing it and buying one from a wrecker?

N_Jay

The motor is a 12volt motor, and if you have a few alligator clips you can make it run and check.
the sensor is a variable resistor, so you can look at that also.
The latches have switches, do you can test those also.

Beav

Now I’m really confused!
Got the motor out, connected it to the battery and it runs like a charm! It seems to work perfectly rotating the gear in either direction. I’m thinking with a small electric motor like this it either works or it doesn’t right?
Next I reconnected all the wiring, all except the final plug going into the motor and when the trunk close button is pressed I get power coming to the plug that would normally be plugged into the motor. Is this exact voltage critical?
On a side note when the motor is completely installed and connected but with the arm to the trunk hinge disconnected, press the button and the arm moves about .125”. It is as if with no resistance from the trunk springs the motor is trying to spin.
Hope this all makes sense! Thank you!!

Beav

N_Jay,
When you say the sensor is a variable resistor I’m assuming you are referring to the potentiometer sensor with the white plastic arm attached (2118201597)? How would I test that?
Also could it be the Trunk Control Module (2118703026)?
Thank you!!!

N_Jay

You have to put an ohm meter across the pins and move it.
I did not remove my motor to test (and hit my head with the trunk lid)
It "could" be the controller, hence the fact I have an extra.

As I said, there are switches in the latches that with some careful work can be tested with an ohmmeter.
There is also a motor in the lower latch, but it sounds like that is working in your case.

I never did find out what was wrong with mine, but when in failure mode the trunk close button was not lit, and when working fine was lit.

I think using the escape button seemed to be part of what got it all back in sync and working.

Beav

Thanks for all your support N_Jay!
I am working on my moms 03 E500 but I also have a 2005 E55 with auto trunk closer. In the process of trying to test the the various components of course I broke a plastic part on the potentiometer. So I said F it and took the same part off my E55 and tried it on the E500, no luck. Then I decided it was easy enough to swap out the control unit so I put that on the E500 and voila it seems to work!!!
Now, the trunk will only open half way!!! I tried resetting it per manual instructions by pressing and holding the red button longer than 5 seconds but that doesn’t work. I’ve tried it dozens of times in subtle different ways but still only opens half way. On the 03 this cannot be changed by way of the steering wheel controls and menus in the instrument cluster. My mom took the car to our trusty indy Mercedes guy and he reset the system several times on his computer but still no luck. I’ve now read dozens of threads on this subject of the trunk only closing part way and I feel like I have tried everything!! It’s my understanding that all of these parts are fully cross compatible.
Please help me finally finish this ridiculous project!!!

jimbo1763

Wife came back from the grocery store, unloaded groceries from the trunk and went inside. Shortly after that she heard the sound of the trunk opening itself in the garage. I came home to find both taillights and the third brake light flickering. Sounds like the wiring harness to me. I will take a look tomorrow. I opened and closed the trunk a few times and got the lights to cut off, so I am pretty confident as to the problem (I hope those are not famous last words!).

I thought the trunk opening itself was pretty sporty, though.

Adt

thanks so much - if I can do this it’s a really simple fix !

Pitek

Hi Everyone,
I wanted to say thank you to hbamark and everyone else who added and shared the solution (e.g. description, steps, and photos) to the existing problem.
Two days ago, I experienced the exact same problem after putting my groceries into the trunk and closing it. I strongly believe that the freezing temperatures (-19 C) with the killing windchill (-25 C = -13 F) added to the inevitable problem.
I turned for help in this forum. I quickly found the solution here.
I allowed myself to throw in one photo of the past and bad memory for your review guys.
Then, I applied the solution. It is all working now!



Severed BROWN wire.

Thank you again!!!

Pitek

Benzconvert

Nine years later and still saving the day! Thanks hbamark. An intermittent problem on 2009 e350 for the last year until it finally quit entirely. Trunk release, trunk light, and license plate light. I read your post and went right to the break. Brown wire just held together by the insulation so it would work and then go open. I never would have found this it was so hard to see. I was ready to bite the bullet and go to the dealer, but with this post I found it in 20 minutes. Thanks to everybody who contribute to this site

Studio5c

Innova801

eaglehawaii

Aloha,

Thank you very much for this thread.

This problem just happened to my car today.

Found this post and found the problem ... brown wire broken at the pinch point where the tie wrap secured the plastic wire loom to the trunk lid left arm.

Easy and no cost fix because of this thread.

Mahalo nui loa.

msavitt

wow !!!
no center brake light, power trunk release or license plate lights
brown wire cut, took 5 mins to fix, great tip!
never believe in coincidences, right?

Martin OC CA

mampersat

Same problem, same fix. It seemed like either a piece of the brown wire was missing, or it was shorter than the rest of the wires in the harness. I added a couple inches of wire, soldered both ends, shrink wrapped and BOOM! Everything works again.
Thanks from 10 yrs after your initial post.
M@

Oliboro100

Thank you for this post. However Come on Mercedes-Benz seriously it’s been a common problem for E-class owners for how manny years? And there is no recall.... that’s pretty bad for such a quality brand I experienced this issue slowly with the interior trunk lights not working. Then the license plate trunk lights went out sometimes when trunk opening and closing. Another trunk has stopped working completely and all those three warning lights are on. Also the easy access lock and unlock button stopped working on the rear passenger door handle drivers side. I’m wondering if that is also tied in with this crap. Unbelievable Mercedes-Benz. Why would they put wiring in a place where it involves lots of movement.... Mercedes Benz should take full responsibility. Hey guys is there a permanent fix to this or will there always be this issue? I’m seriously pissed.

N_Jay

Chill!
The trunk issue is completely separate from the door issue.
The door latch issue is the rubber seal behind the button breaking letting water into the switch assembly. Yes they should probably last longer than they do.
The trunk is the wire where the hinge bends when the trunk opens the wire has to bend The only thing they could do is make sliding contacts or a loop of wire either of those create other issues.
Just remember, every product is a compromise.

How many miles did your car go before the trunk showed up as a problem, how many times was it open and closed?
Nothing lasts forever.

mlim24

Thank you everyone in this post especially hbamark!!! Exactly as you all have described. Took a few minutes to find the broken wire, but it was right about where you suggested and it was the brown one. Terrible design flaw MB.

Mental

Sorry to zombie up this thread, but this was so great. Read the initial post, fixed it in the parking lot at work. Its for an E Class, but I am sure you all know a CLS is just a swoopier E Class.

So Thanks!!