PJE

I just fixed this on my 2008 E350 4matic keyless go. There are two reasons that the brown wire is the most likely one to break first. 1. That wire is a common return ground for all the circuits, therefore it is thicker and stiffer than the smaller supply wires adjacent to it. MB chose to use a very stiff wire type for this that is less able to handle the repeated bending stress. The smaller wires are more flexible. 2. The bending forces are concentrated over a very short length due to a bad design. The large plastic cover over the arm ends right where the flexible plastic wire shield starts. That flexible corrugated wire cover should have extended farther under the plastic arm cover. MB's design allows the wire bundle to flex far too much at that stress point. When the trunk opens and closes all the wire bending is concentrated at that spot instead of being spread out over a longer length of the wires. I did two things to address this. First, I spliced in a short extra length of flexible multi strand copper wire to create a more resilient joint. Second I added another loose wire tie around the corrugated wire bundle cover at the point where the trunk gear bracket and spring attach to the arm. This prevents all the bending from happening at the point where the wires leave the plastic plastic arm cover. I left this tie loose so the wire bundle could slide and not create a new sharp bending point . This will spread out the bending arc of the wires over a longer distance. Understanding the cause of a problem helps engineer a longer term fix.

Radixon67

[QUOTE=hbamark;3694210]Hi All,

If your vehicle has lost power to the trunk unit, and lights, there is a very simple fix. This is fairly common problem on W211 models. The wires get caught it trunk hardware and get severed. The dealer wanted to charge me $250 for something that took me 20 minutes and less that $10 to complete. Here's what I did.

1. Use the key to manually open the trunk.
2. Remove two plastic pins holding carpet/panel on the driver side of trunk. Pull carpet/panel away carefully.
3. Remove plastic cover on left trunk hinge by unfastening pin at top of cover.
4. Follow the wires until you find where they are severed.
5. Strip wires slightly.
6. Put a piece of shrink tubing over one side of the wires.
7. twist severed wires back together where you stripped and exposed the copper.
8. Solder the wires.
9. Pull the shrink tubing down over the exposed copper.
10. Heat the tubing so that it shrinks around the exposed wire.
11. rewrap wire so that it follows the left hinge in a manner that is will not get cut again. (I wrapped the at risk area in duct tape, not pretty, but it was effective).
12. Reinstall Panels.

Sorry for the lack of pictures, but this is a real easy fix. I hope this procedure saves some $$$ for someone.[/QUO




i have no power to any rear lights or trunk release can’t find any broken wires

mig1980

Can someone point me to what gauge wire this is (specifically the brown ground) and where can I pick some up? I need to add a piece of wire to extend it a bit but figure out the gauge.

mampersat

I used 22 gauge. Got it on amazon.

mig1980

Thank you. Is that the same gauge as the wire that is there?

mig1980

Any input on this? Would like to get this fixed but unsure if the wire that is there is 22 AWG.

cetialpha5

Just use a butt splice connector. You just push in both ends.

https://www.homedepot.com/p/Ideal-Sp...342S/202894306

Happy matt

Happy matt o my word having read the instructions you gave it took me no more than ten mins start to finnish so chuffed .

Alandbecca

Hiya, I have done all this following installation of a new Rear SAM unit and the switch on the drivers door stays red preventing the boot (trunk) from closing. When I separate the brown wires again the boot closes but 3rd brake light is then out. I’m guessing there’s a short circuit somewhere so any ideas please?

PJE

When I made this repair I fixed the real problem. MB chose wire that was too sfiff and it is not mechanical breakage, it is fatigue from bending. You can have a conductor break and have the insulation still intact on the smaller wires. You need to check each wire carefully. for my repairs I added a 3" length of wire in a loop to reconnect them. This distributes the bending stress over the entire loop which will prevent future breaks. If you pull or flex each conductor it may help you find the hidden breaks. I had two wires broken. The large one and one smaller one still insulated. Hope this helps.

martonjhon

Quick fix for W211 models with trunk power and light issues. Manual trunk opening, remove panels, find severed wires, strip and solder them, use shrink tubing, secure wiring, reinstall panels. Saved me money, hope it helps someone else! I experienced this myself and the dealer quoted me $250, but I managed to fix it in 20 minutes for less than $10. Here's what I did

PJE

When this happened to me, I did not just re-solder the wire that broke. The wire broke where it did because that's where it bends and it was too stiff for that application. Instead I soldered in a loop of wire about 3 inches in diameter and wire tied each end to its respective bundle, but let the loop "float". This distributes the bending stresses over a much longer length of wire to prevent any recurrence.

Doingmybest

Bingo!

2 weeks after purchase same thing. 2 wires broken deep behind left trunk shell. Should’ve came here 1st.

Anyhow, thank you!

edbso

Thank you hbamark:

Had the same symptoms of "no 3rd brake light" and had to use the key to get into the trunk.
The brown wire was completely severed.
Easy fix once you know what to do. Thanks again

sschenec

I had the broken wire and it fixed my license lights, third break light and now the motor on the lock makes noise, but the trunk will not open with fob or door button still - everything else fixed when the brown wire was re-attached. Could there be something else?

N_Jay

check for another broken wire.

Doingmybest

sschenec

Two wires were broken in my situ. Check again every wire in bundle...or two places on same wire...or cracked wire yet held together by casing.

sschenec

The plastic gear in my trunk actuator broke, if we can figure out how to replace just the gear, it is $12, but a lot more if we have to replace the whole actuator... I just can't find a youtube that shows me how ....

nd-photo.nl

This was the situation in my 2005 CLS55 W219

bernmeister

Just to say thanks for the post, great fix. It seems to almost always be the brown wire by the hinge that breaks. Other wires showed signs of being close to breaking, fixed them as well.

bigtimeny1