E39 Electrical Problems Traced to Trunk Lid Harness Wire Chafing (DIY Diagnostic)

Originally Posted by dvsgene

I would splice and solder back the sheared or broken wires, re-wrap with electrical tape and put a split wire loom or spiral around the harness (space permitting) to protect it from future damage.

We definitely need a good DIY repair fix for multiple broken wires.

Of course, the "right" way would be to buy a whole new loom but it seems nobody does this. Every dealership I checked says they never sell it (they couldn't even tell me which loom it is in the realoem diagram above).

Most people splice and wrap the wires.

The suggestion to make 'em longer would work, but, only if we do ALL 13 wires.

So, it will be nice to see pictures of other people's results. I still have mine just wrapped with electrical tape ... I'm waiting for all the good fixit suggestions to come in!

If one would literally grease that rubber grommet inside, where the wires are routed, would that slow down the rubbing/chafing process, or is this a bad idea? (One could grease the MF twice a year or so)

Originally Posted by doru

If one would literally grease that rubber grommet inside, where the wires are routed, would that slow down the rubbing/chafing process, or is this a bad idea? (One could grease the MF twice a year or so)

Doru, I think that's a good idea but some grease or lubrication can eat away at rubber or if it begins to seep into the electrical tape the adhesive of the tape unravels which is why is suggested replacing the grommet with a new one. I'm sure it's less than $5 even at the dealer. Follow that with the split loom to protect the wires and it should be good.

After my 1st initial repair didn't hold (I didn't solder broken connections, I didn't lengthen wires), my Uncle and I spent 2 hours putting and soldering in extensions and re-wrapping the loom. It has been fine for about 2 mos. now, but I will check it later this week for evidence of cutting to the wires that were not lenghtened and report back. If you are buying a new harness, I would check and see if the total length is longer than stock. If not, then you will run into the same issues in time. It really seems they didn't provide enough length. Maybe there was a change in the trunk hinge design after the wiring length was deteremined? Because it really seems it is the last inch or so when opening the deck lid past 90 degrees that causes the stress.

Originally Posted by aliaw528

After my 1st initial repair didn't hold (I didn't solder broken connections, I didn't lengthen wires), my Uncle and I spent 2 hours putting and soldering in extensions and re-wrapping the loom. It has been fine for about 2 mos. now, but I will check it later this week for evidence of cutting to the wires that were not lenghtened and report back. If you are buying a new harness, I would check and see if the total length is longer than stock. If not, then you will run into the same issues in time. It really seems they didn't provide enough length. Maybe there was a change in the trunk hinge design after the wiring length was deteremined? Because it really seems it is the last inch or so when opening the deck lid past 90 degrees that causes the stress.

Maybe the fix is to add 3-4 inches/wire then? (solder, and wrap each one, then back in the grommet?)

Originally Posted by doru

Maybe the fix is to add 3-4 inches/wire then? (solder, and wrap each one, then back in the grommet?)

I think that would be ideal.

For the cross-reference record, here is another suggestion as to how to fix the trunk loom without actually replacing the entire loom itself:

"... my dad used to run a TV/radio repair shop, and he did this a few times when fixing broken wires: He would solder the wire back together, then lay the repair lengthwise on a piece of black electrical tape. He would then put some 5-minute epoxy on the repair, and wrap the tape around the glued area like a cylinder. After the glue had dried, he would wrap it with electrical tape again. It worked great, but was somewhat inflexible. In this application, that could lead to problems down the line.

I have been thinking about doing the same, except instead of epoxy, using RTV, and using shrinkwrap instead of electrical tape. This would be somewhat flexible, protected from he elements, and quite strong."

The quote above is from Philboski in the electrical gremlins thread here.

Looks like we can add "battery drain" issues (not otherwise related to the FSU) to the list of electrical gremlins that might point to frayed or broken trunk lid loom harness wires ...

this has caused me so many more issues than listed! i did have the harness repaired under warranty at the dealership and 2years later the same thing only they said it wasnt covered because the car was out of warranty and their work was only covered for a year, idk! they offered to replace the entire harness for around $500! its crazy that after two years to have the same prob again. they told me that bmw only alows them to splice new wires and not replace the entire harness! but i do know why it happened on my car atleast, its that the harness folds and gets pinched every time the trunk gets closed. i never put two in two together when i would see the little black rubber sticking out of the trunk lid and just thought it to be a rubber lining or seal on the trunk or window seal! one day it was bugging me and i looked further into it and realized it was the harness! so i removed the rubber boot pulled it down to expose the wires and they were all cracked except for one wire and one was completely separated , this would explain why my trunk would not open with the key or the button inside the car and the trunk lights didnt work and the alarm wouldnt beep when set and the alarm would always go off for no reason and the battery would suddenly be dead for no apparant reason and the central lock would sometimes not work and the licence plate light would sometimes stay on when the car was off and the trunk could only be opened with the key, hmmm! what else im sure there is more! so basically after finding this out and taking it back to the dealer and having them tell me that it wasnt covered and it would be $500 i decided to rewire it the best i could! i spliced and reconnected the wires and taped them real good and right away the trunk worked and all my probs were fixed, so i thought! now about one month later its starting all over again, i havent looked at the wires but im sure they are coming undone or something!! evrything is fine except the battery issues! my car just randomly has a drained battery, for no reason its just dead after i drive it all day with no probs. does anyone know if this could be causing the battery drain or shorting it out or does the car have a theft protection where the battery disarms the car from starting! it will start from a jump everytime and the battery was replaced two years ago! evrything checks out fine as far as the alternator goes! can a cracked windshield set the alarm off? any help or suggestions would be great! i love this car and it drives great just some minor issues!

Originally Posted by bluebee

Looks like we can add "battery drain" issues (not otherwise related to the FSU) to the list of electrical gremlins that might point to frayed or broken trunk lid loom harness wires ...

what may i ask is the fsu? im not familiar with the codes or initials! sorry!!

hello, can u please tell more of the issues you were having with your car so i can try and diagnose my probs to yours and maybe my problems are hopefully because of the trunk wiring harness! this is driving me crazy!! thanks!!

Originally Posted by gemnilvr

what may i ask is the fsu? im not familiar with the codes or initials! sorry!!

FSU aka Final Stage Unit. Symptom is blower still on after engine off or blower fan not working when engine on.

Originally Posted by dvsgene

FSU aka Final Stage Unit. Symptom is blower still on after engine off or blower fan not working when engine on.

Besides that canonical Elvis thread, I also had an FSU-solved problem of the battery going dead intermittently which "solved itself" when I replaced the FSU.

My blower was barely on when the car was off ... I mean only a whisper could faintly be heard ... and even then I wasn't sure it was the blower itself that was running and killing the battery ... but, with the new FSU (aka FSR) the dead-battery problem resolved itself instantly.

http://www.bimmerfest.com/forums/sho...3&postcount=12

I had this same problem when I bought the wife's car 2 years ago I came out to a dead battery 2x, the trunk would open when I turned on headlights and lights would flicker in car/glovebox, speed/key in the ignition chime worked sometimes. once while opening trunk chime kicked in then when I closed it stopped so I reached for the harness and BAM frayed wiring...guess what, her car is TOPAZ like so many others...hmmmmm

rewrapped all the wires individually with electrical tape and then rewrapped the the whole bundle then slipped boot back over...no probs since(yet). The position of boot is very bad and I even pointed it out to seller of car when it was bought, because I could not understand why the harness was so visible with trunk closed

I found this a few years back when I was thinking I had to replace yet another trunk latch solenoid, but found it was intermittent. That location is bound to break in everyone's. BTW, I had to get into the trunk from the back seat because I couldn't open the trunk.

BobZ

Just checked my trunk harness and repaired 1 wire. I was getting a "trunklid open" message, and prior to that every once in a while the parking lights would flash continuously after disarming the alarm. When that happened it was like the someone pressed the hazard lights.

My E36 had this problem prior to my owning it and was repaired by the dealer for some ungodly sum of money...

Hi,
Does anyone know what gauge wire is used on the trunk wires? I was going to splice the broken ones. Thanks

I spliced about 9 wires using a wire that just looked close in size to the freyed wires. All electrical problems ended.

Nice info, I'll make sure to check mine!

This one BMW brown ground wire video from an ABS traction-control thread is quite compelling to show what electrical gremlins a single errant brown ground wire could cause.

Imagine ...

I just ran into this online "WDS BMW Wiring Diagram System - Model 5 E39 from 09/98" from "http://spaghetticoder.org/bmw/wds/e39new".

I'm having trouble finding it but maybe someone can use this reputed BMW E39 online wiring diagram program to show us what the remaining trunk-lid wiring harness loom wires connect to?

02. Red/black line = ?
13. Brown/blue line = ?

How do you guys get access to the trunk loom wires themselves?

This trunk-loom fix isn't as easy as it at first appeared!

Yesterday, I tried for an hour to pull the trunk loom down enough to get to both sides of all the broken wires but to no avail.

Then, just as unsuccessfully, I tried pulling the other end out of the body of the car, only to find that it has a longer smaller tube inside that is holding fast!

So, I resorted to scissors!

But how do YOU guys get to the wires in the trunk loom w/o destroying it?

BTW:
While performing open loom surgery, I ended up slicing the brown (ground) wire that apparently handles the key-fob and underside lid handle unlock of the trunk and the lock chirp (now I have to open the trunk manually with the key turned left in the lock cylinder).

I guess everyone slices the hose to fix the wires.

As for the wires, does anyone know what gauge they are?

Update:
I'm still in the middle of this job ... with the loom and wires cut ... and taped.

- Dunno if I'll solder because that would just make a break point
- Can't wire-nut them because they won't fit in the loom (satiated snake)
- I can't just strand them together because they'll pull apart invariably
- I'd replace the loom if I could find the part number & if the price was ok
- Sure would be nice to see a picture of someone else's results (how they did it)

You may need to speak to a dealer parts tech for help finding a part number and cost for the repair harness. I know they exist for several various BMW models, they must offer it for the E39. I just tried Realoem, and had no luck finding it either...