BimmerFest BMW Forum banner
252K views 152 replies 57 participants last post by  00323ciE46 
#1 ·
I knew this day would come.

Earlier this week, the trunk refused to open when I hit the interior trunk release or the button on the key. I could only open it manually by turning the key in the keyhole. The trunk interior lights didn't come on when I opened the trunk, and the trunk-open light in the instrument cluster was continually lit. It occasionally flickered over hard bumps.

I'd done this repair once already - several years ago, on my 1997 328i. (See signature for details.) When the trunk lid wires on that car frayed and started to cause short-circuits, the central locking system fuse kept blowing. My E46 didn't do anything that exciting, thankfully.

After some exploration today, I found that the ground wire for the trunk lock actuator was completely severed after years of bending and kinking. See the attached photo. All of the other wires in the bundle (16 total) are still intact, but they're bound to start fraying too. Since there doesn't seem to be an affordably priced E46 replacement harness available at BMW dealers, I'm going to splice all new wires into the part of the harness that passes from the body to the trunk lid. I already have a new rubber cover and splice connectors; I just need to purchase the wire. The wires in the trunk lid are all 18-gauge and smaller, and the wire I have on hand is just too big for 16 of them to pass through the rubber cover. For now, I've spliced a short length of new wire to replace the broken wire, and the trunk lock and trunk lights are working.

I will update this thread with observations and tips after I complete my repair. If you're having trouble with your license plate lights, reverse lights, or the trunk lock actuator, you might want to check for frayed wires.
 

Attachments

See less See more
1
#2 ·
Yow !!!! Homey don`t like no Crispy Critters !


As they say down in Miami:

"Dass focked opp, Mang !"
 
#3 ·
As they say down in Miami:

"Dass focked opp, Mang !"
Yes, it is! Actually, this damage is pretty mild compared to some of the pictures I've seen on other forums.

Does anyone have any thoughts on whether PTFE-insulated wire would fare better in this application than standard automotive PVC- or XLPE-insulated wire? As far as I can tell, the factory stuff is PVC. It seems that PTFE would be tougher and better than PVC at retaining its flexibility at low temperatures.
 
#5 ·
In E39, Bluebee has a great write up for trunk wire look.
 
#6 ·
I knew this day would come.

Earlier this week, the trunk refused to open when I hit the interior trunk release or the button on the key. I could only open it manually by turning the key in the keyhole. The trunk interior lights didn't come on when I opened the trunk, and the trunk-open light in the instrument cluster was continually lit. It occasionally flickered over hard bumps.

I'd done this repair once already - several years ago, on my 1997 328i. (See signature for details.) When the trunk lid wires on that car frayed and started to cause short-circuits, the central locking system fuse kept blowing. My E46 didn't do anything that exciting, thankfully.

After some exploration today, I found that the ground wire for the trunk lock actuator was completely severed after years of bending and kinking. See the attached photo. All of the other wires in the bundle (16 total) are still intact, but they're bound to start fraying too. Since there doesn't seem to be an affordably priced E46 replacement harness available at BMW dealers, I'm going to splice all new wires into the part of the harness that passes from the body to the trunk lid. I already have a new rubber cover and splice connectors; I just need to purchase the wire. The wires in the trunk lid are all 18-gauge and smaller, and the wire I have on hand is just too big for 16 of them to pass through the rubber cover. For now, I've spliced a short length of new wire to replace the broken wire, and the trunk lock and trunk lights are working.

I will update this thread with observations and tips after I complete my repair. If you're having trouble with your license plate lights, reverse lights, or the trunk lock actuator, you might want to check for frayed wires.
Good stuff to know!:thumbup:
 
#9 ·
GP

I agree with jcourcoul that it will not stick to teflon. Kind of makes my orig. recommendation a moot point. (facepalm) I do like jc's solution though with the rubber stretch tape. May be the only solution if you want to use the teflon coated wire. In any case, I don't think you will ever have to do this repair again. Good luck, and keep us updated on how it goes. I'm sure I'll be there soon too, as my Wife just loves to put the purse in the trunk on the vert.
 
#140 ·
trunk repair add on



The tape described is available in the plumbing section at Lowes and Home Depot. It is called Stretch and Seal Tape and a roll runs about $7 for about ten feet. I used it on hundred year old water supply pipe about five years ago, and it worked and is still working on a small crack in our lead water supply pipe. It is a silicon blend of some sort, and remains pliant for a long time.
 
#12 ·
Try to get one of the MILSPEC-approved variety....that`s top-of-the line stuff.
 
#14 ·
And now I will bore everyone with talk of wire... :snooze:

PTFE-Insulated Wire
In case anyone else with frayed trunk wiring is looking to use Teflon-insulated wire for this repair, I did some searching yesterday for ways to make waterproof splices that will stick to the surface of PTFE. It's possible to do so by chemically etching the PTFE surface first; after that's done, most conventional adhesives will work. Here's an example of an etching process, which seems pretty time-consuming.

Many sources also mention that the use of regular wire strippers on PTFE insulation is likely to nick the silver plating on the copper strands, but this page recommends an inexpensive Imperial brand stripper that you can get at McMaster-Carr.

XLPE-Insulated Wire
I mentioned XLPE (crosslinked polyethylene) insulation in an earlier post - it meets SAE standards for wiring in the engine bay (-51 deg. C to 125 deg. C). It's readily available from several sources, including KayJay Company and Pegasus Auto Racing.

If you're going to go with XLPE, you need to get the thinnest specified insulation (TXL) in order to make a bundle that passes through the rubber covering from the body to the trunk lid. The 18-gauge XLPE-insulated wire I have in the garage is apparently either GXL or SXL, the medium and heavy thicknesses. These wires make too big a bundle.

XLPVC-Insulated Wire
There's also irradiated PVC, sometimes abbreviated XLPVC. It's PVC that has been exposed to electron beam radiation, making it tougher, more heat-resistant, and more abrasion-resistant than regular PVC. This wire (-55 deg. C. to 80 deg. C) can't take engine bay heat like XLPE can, but the thickness of XLPVC insulation is comparable to that of PTFE insulation, which means I'll be able to keep the bundle diameter down. A local supplier has seven different colors of a mil-spec XLPVC wire available. It's about one-third the cost of Teflon wire, and it doesn't require chemical etching to get heat shrink adhesives to bond to it.

So it looks like I'll be going with the mil-spec XLPVC-insulated wire instead of Teflon. I have no doubt that Teflon would last longer in this application, but XLPVC would allow me to make waterproof splices much more easily and at lower cost.
 
#21 ·
GP - Interesting thread. Sorry about your misfortune, but I'm glad it didn't do much damage, and we all appreciate your sharing your experience on the wire bundle repair.

I have one small favor to ask. Could you please identify which wires control the back-up lights? I'm planning to install a back-up sensor on my daughter's 04 325i, but am stuck at the wiring step, and I don't have a Bentley manual (yes, I know, I need to get one, but with my wife's new business still struggling to keep its head above water, money is very tight).

Thanks very much.
 
#22 ·
Could you please identify which wires control the back-up lights?
Dunno how much this helps for the E46, but we identified the innervation point of all 13 wires in the E39 trunk wiring loom over here.
- E39 Electrical Problems Traced to Trunk Lid Harness Wire Chafing (DIY Diagnostic)

If you don't get an answer specific for the E46, the technique we used to identify the wires' innervation points should be useful to you also.

In addition, the problems that occur when the end points were enervated (by the broken or shorted wires) might also be of use to you.

 

Attachments

#27 ·
Thanks very much. Although I suppose all it would take is to get access to the reverse light (anybody know if this should be done from the outside by removing the lenses, or from inside the trunk by removing the paneling on the inside of the trunk lid?), and matching up the wiring there with what's in the bundle, right...?
 
#28 ·
all it would take is to get access to the reverse light
That would solve ONE problem but not the BIG PICTURE. :)

G. P. Burdell and I were talking about adding value to the big picture by identifying ALL the wires on the E46 (just as we did on the E39).

Once that happens, it's much easier to determine which problems can be related to the trunk loom - and - which will have no bearing on the trunk loom.

It almost never makes sense to solve the little picture ... that's the whole point of the forums ... to increase knowledge and add value in every post!

Good luck!
 
#31 · (Edited)
Update:

I finally found the time to rebuild my car's trunk wire harness. I say that I rebuilt the harness because, once I was done, there wasn't much left of the old harness. Here's my writeup for anyone wanting to do the same.

Introduction

This work took me an entire day from start to finish. I will readily admit that I'm not the fastest DIYer; I frequently stop and take the time to document the process with written notes and plenty of photographs for future reference. On this task, I checked and re-checked my work several times to make sure I spliced the right wires to each other. These checks involved numbering the wires and testing for continuity, both in the car and on the bench.

The temporary repair I made about a month ago held just fine, but I had to make an inline splice right in the area of the harness where the original ground wire had broken. The splice would eventually have broken, or it would have chafed against the other wires in the harness (one of which was looking rather kinked already) and caused more damage. Furthermore, in order to find the broken wire, I had cut into the existing corrugated EPDM rubber cover that protects the harness and seals out water. I wasn't able to locate a complete replacement harness in the BMW parts catalog, so I decided to replace the entire wire bundle that passes from the body to the trunk lid.

Disclaimer

I AM NOT A BMW TECHNICIAN. I am sharing my experience based on the repair I made to my E46 sedan. Depending on the year and configuration of your vehicle, your car's wiring may vary. I will not be responsible for any damage or injury that results from following anything I have posted in this thread. Verify part numbers before you purchase your own materials. It is your responsibility to also verify technical information with a trusted source, such as BMW TIS, your copy of the Bentley Publishers repair manual, or a reputable mechanic. If you are not comfortable with doing this work on your own car, I recommend that you seek the assistance of an experienced friend or your mechanic. Use appropriate safety measures and have proper ventilation when working with heat shrink materials inside the trunk. As always, you are welcome to do things differently and discuss your method here.

Materials

Most of these products, except for the ones with BMW part numbers, are available from vendors such as McMaster-Carr.

  • Wire. I used irradiated PVC (XLPVC) insulated wire in 18- and 20-gauge sizes.
  • 18-to-22-gauge splices. I chose butt splices that are insulated with adhesive-lined heat shrink for the best moisture resistance. Others may choose to solder and heat shrink.
  • Zip ties
  • Wire markers. I have a book of self-adhesive, preprinted Tyvek wire markers that I used to number the wires sequentially, from 1 to 16.
  • Electrical tape. Not for wrapping the entire harness, but used in small quantities for bundling wires together at certain points.
  • Fabric tape. A 15-meter (45-foot) roll is BMW P/N 61 13 6 908 716. Dealer list is $17.72. The factory harness, along with most other interior wire harnesses in the car, is wrapped in a fabric tape that's similar to this tape.
  • Rubber covering. The replacement for the cover for a sedan is BMW P/N 61 13 8 366 627. Dealer list price as of the date of this posting is $6.38.
  • Painter's tape

Tools

  • Common sense
  • Patience
  • Bentley manual
  • Safety glasses
  • Headlamp
  • Disposable gloves
  • Wire cutter & stripper tool
  • Crimping tools
  • String
  • Ratchet and 10mm socket
  • Plastic pry tool
  • Phillips head screwdriver
  • Multimeter
  • Heat gun

The Process

The basic steps involved were:

  1. Disconnect battery. Disassemble trunk lid and right side of trunk.
  2. Identify and number wires and connectors.
  3. Pull old harness out of trunk lid and into trunk.
  4. Test for continuity to confirm wire assignments.
  5. Cut old wire harness out of car.
  6. Build new harness on the bench from pigtails of existing connectors.
  7. Test continuity of new harness on the bench.
  8. Reinstall new harness into trunk and trunk lid.
  9. Splice new harness into existing wires in trunk.
  10. Reconnect battery and test trunk lights, license plate lights, and central locking functions.
  11. Put trunk back together.

Observations

  • This is not a job to rush through. I had to get to work the next morning, and splicing the wrong wires together could have shorted out a component, blown fuses, and resulted in a lot of cussing.
  • Before starting the work, I wrote down and numbered the wires, then researched the Bentley manual electrical diagrams to make sure that I knew the size of each wire and the appropriate size of the wire I would splice in. The wire sizes in the BMW literature (and hence the Bentley manual) are in metric units, so I did a Google search to find a table that lists metric and equivalent SAE and AWG wire sizes. SAE and AWG wire sizes are not the same; AWG wire sizes are slightly larger than SAE.
  • I bought a few different colors of 18- and 20-gauge wire and planned the colors I would use for each splice. For example, I replaced all of the brown ground wires with black wire. It's not completely necessary, but it helped me to identify the wires in the rebuilt harness a little more easily.
  • The existing wire harness is wrapped in a fabric tape whose adhesive has broken down with age and exposure to heat. Just touching the tape left my hands feeling sticky. For the more involved work with the old harness, I wore disposable gloves to keep the goop off of my hands.
  • Before pulling the old harness from the trunk lid, I tied a piece of string to the last connector on the harness. I pulled the old harness out of the trunk lid and untied the string only after it had entered the trunk. This piece of string was my pull cord that would help me to feed the rebuilt harness into the trunk lid.
  • Very Important Thing No. 1: Before cutting the old harness out of the car, I checked each wire for continuity. I picked a portion of the old harness that wouldn't remain in the car and stripped the insulation off of each wire, one by one, to check continuity and number the wires in the trunk. The good news is that the majority of the wires are unique in terms of their insulation and stripe colors, and the grounds that don't go back to the LCM or the General Module all go to a single ground point (X498) inside the trunk.
  • I rebuilt the harness on the bench. I put strips of painter's tape down on the bench and traced the old harness onto the tape with a marker. I marked where each branch came off of the main harness and noted which connector/device was on that branch. Next, I marked the locations of the splices I would make for each branch. I cut the old connectors, each with lots of the original wire still attached, off of the harness and discarded the old harness. I cleaned the old adhesive off of the pigtails and spliced the new wires to these pigtails, one by one, according to the "map" I had drawn on the tape on the bench.
  • After checking continuity for a second time, I wrapped the completed harness in fabric tape. In addition to protecting the harness from chafing against the sharp edges of the trunk lid as I reinstalled it, wrapping the new harness in this tape helps to prevent it from rattling around in there. The old harness didn't have a lot of tape wrapping the portion where the wires tend to kink and break. I wrapped this area completely in an effort to give the wires more support.
  • Very Important Thing No. 2: The hole where the wires enter the trunk lid isn't very large. Splicing all 16 wires at one point along the harness and then feeding it back into the trunk would not have worked, because the resulting bundle would not have been able to fit through that hole. I staggered the splices so that only three or four passed through the hole at a given time.
  • I left plenty of excess wire on the trunk side of the rebuilt harness so that I would have lots of slack inside the trunk. More slack meant that I could make splices more easily without bringing the heat gun too close to paint, carpet, or plastic inside the trunk. I wound up with about a foot of slack inside the trunk.
  • 16 wires x 2 splices per wire x 2 crimps per splice = 64 crimps. A ratcheting crimp tool saved me from some serious hand fatigue.
  • Very Important Thing No. 3: Before making splices in the trunk, I made sure to put the new rubber cover on the rebuilt harness! It would have been very bad if I had forgotten to put it on there before making all of those splices.
  • The inside of the trunk lid is full of sharp surfaces. I didn't wear gloves while feeding the rebuilt harness into the trunk lid, and my fingers had more than a few tiny cuts by the time I was finished. Disposable gloves might help prevent this from happening.
  • I had a fire extinguisher close at hand when applying heat to the splices in the trunk, just in case. The Tyvek wire markers will not survive exposure to a heat gun. When using a heat gun, it helps to have the nozzle attachment that's made for use with heat shrink.
  • After finishing all of the splices and testing the trunk lid devices, I tied back the bundle with zip ties to prevent strain on the splices.

Whew! That was a lot of work, but now I have all new wires passing from the body to the trunk lid. We'll see how long the new bundle and its tougher-than-regular-PVC insulation lasts. BMW could make this repair a lot easier and more convenient if they would produce and sell an affordable replacement harness like they did for the E36.
 

Attachments

#39 · (Edited)
Bumping up an old thread: http://realoem.com/bmw/showparts.do?model=BL93&mospid=47714&btnr=61_1237&hg=61&fg=10 is #3 a replacement harness for this? Or is that something else?
I think that's the same part I asked our local dealer parts guy about, and he didn't think it was a replacement.

Thankfully my wires are still good, but I'd really rather not go through the trouble of rewiring it myself when the time does come. Any suggestions as to what can be done to relieve the stress?
Short of never opening your trunk, I'm not sure that anything can be done to relieve the stress. The wires have to unfold and fold every time you open and close the trunk.
 
#40 ·
Since you can't relieve the stress, would it make sense just to wrap electrical tape over the wires to help reinforce them and help prevent rubbing?
 
#42 ·
Rubbing doesn't seem to be the problem; it's the flexing that weakens the individual wires in the bundle.

That's why the maker uses fabric tape instead. Longer lasting and doesn't gum things up as bad as deteriorated vinyl tape.
The fabric tape makes quite a mess, too, when its adhesive breaks down. Taking the old harness out and marking the wires was a sticky PITA.
 
#41 ·
That's why the maker uses fabric tape instead. Longer lasting and doesn't gum things up as bad as deteriorated vinyl tape.

All old cars develop the 'bad trunk harness wiring' sindrome. No escape. In my old Fords, I've had lasting success by wrapping the harness in rubber self-amalgamating tape. After a day or two, it fuses into a seamless rubber 'tube' that closely encases and protects the wires. The UK-made MotorMite brand I find at AutoZone is reasonably thin and doesn't increase harness diameter too much. Don't know if a harness wrapped like that could be teased thru the trunk access holes and rubber hose in the Bimmers.
 
#44 ·
This the wiring harnes on the right side?
Yes.

How much would this cost me if I were to take it to a dealer or an independent mechanic?
I don't know. Having replaced the wire harness on my previous car, I never bothered to ask a dealer or my local independent.

If you get a repair quote from your local dealer, be sure to find out if they will replace the entire harness with a new one, or if they just plan to splice new wires into the existing harness. It's hard to tell from the parts diagrams whether there's a replacement harness available at a reasonable price.
 
#45 ·
I stickied this thread based on the potential hazard involved and that this is the type of thing that ought to be highlighted as the population of E46s ages (gracefully, of course. :bigpimp: :thumbup:)

Hope that is ok with the OP.
 
#48 ·
Then what type of wire should I get at autozone?
Local auto parts stores don't stock the wire you need for a lasting repair. My rebuilt wire harness is made from XLPVC-insulated wire sourced from McMaster-Carr.
 
#49 ·
On the way to work this morning, the trunk open indicator lit up on the dash. When I arrived at work, had to manually open the trunk with the key. I pulled open one end of the rubber cable cover on the wire harness in the trunk and saw that the brown wire was broken.

I think I'll just temporarily patch together the broken wire this weekend and start ordering the wire to build a replacement harness.
 
#51 ·
Didn't have a chance to make the repair this weekend. It appears that the brown wire is the ground for the interior trunk lights and the automatic trunk release. I just covered the bare ends of the wire with electrical tape to prevent anything from happening. I'll fix this next week sometime.
 
#52 ·
I fix mine with eletrical tape and the light went off and everything works


but now on my Dash, it tells me my license plates lights are out.

Could this be because of the wiring trunk harnes(meaning part of the trunk cables are affiliated with the license plate lights?


PS where can I buy LED license plates ???
 
#53 · (Edited)
but now on my Dash, it tells me my license plates lights are out.

Could this be because of the wiring trunk harnes(meaning part of the trunk cables are affiliated with the license plate lights?
The trunk wire harness supplies power to all of the electrical devices in the trunk lid, so yes, there are wires for the license plate lights in that harness.

First things first - have you checked to make sure the bulbs light up and the contacts are clean?

You may want to revisit your repair job in the near future; electrical tape has a tendency to unravel as the adhesive degrades.
 
#54 ·
Well there was one light brown cable that cut in half, so I spliced it.

But before I did all this, one of my license plate was out. When I spliced it... I didn't get no warnings until two or three days later. At first before I fixed the wiring harness, the red lights would come on and the go off after 2 minutes. But now they are on until the car is turned off.

Is there a tutorial on how to remove the license plates lights?

Or how to check to see if the are working properly(I was going to get some LEDs, but there is no point if the cable are bad)

Sigh...:eek:
 
#55 ·
Or how to check to see if the are working properly(I was going to get some LEDs, but there is no point if the cable are bad)

Sigh...:eek:
I would imagine that you could remove the bulb and check the continuity to see if the bulb has burnt out.

On my trunk, the brown wire broke and I found a couple of the other wires are starting to break. I picked up some wire and I'm planning on repairing this tomorrow. I'm just going to replace the bad wires by replacing the section that runs between the trunk and the trunk lid and splicing in a new wire.

I hope I can get away with only replacing a couple of wires now and that will be it.
 
#56 ·
In split-wire hell...

I have an e46 (2000-328i) and have been dealing with this issue for a while now. About every 3 to 6 months I have pull out my fire-starter soldering iron and just solder the wires back together. This is starting to get tiring. I'm curious about the success of the following:

1) Has anyone replaced the complete wiring harness with a non-home-made (like GP) one?
2) Has anyone replaced individual wires (the whole length). I.e. a single ground wire from end-to-end?
3) Has anyone found correct color-coded wire spools (ie. Blue with the yellow stripe)

GP, when you rebuilt your wire-harness did you use color-coded wires? If not, how do you anticipate repairing split wires ten-years from now (for the sake of argument, let's assume you'll keep this car forever)?

Thanks for any input, info and help anyone can provide.

I will post some pictures of my repair job and explain what I did soon. I will also try to trace through the wiring (I have a Bentley Manual for the e46) and post that soon also.

;-> (consternation)
 
#57 ·
2) Has anyone replaced individual wires (the whole length). I.e. a single ground wire from end-to-end?
Some of the wires originate from the General Module or the Light Control Module in the dash; it would be a major effort to replace the entire run.

GP, when you rebuilt your wire-harness did you use color-coded wires? If not, how do you anticipate repairing split wires ten-years from now (for the sake of argument, let's assume you'll keep this car forever)?
I color-coded the wires to a certain extent. I could have used many more wire colors than I did, but with the ordering minimums at McMaster-Carr, I would have wound up with a lot of excess wire when I was finished. Brown insulation wasn't available for ground wires, so I used black for all of the grounds. I think I used five different colors.

If I should ever have to redo the job, it should be made a little easier by the numbered wire markers I attached to each wire at the connectors and at the splices in the trunk...assuming the markers don't fall off when I open things up. :)
 
#59 ·
GP, a small question, instead of routing through the existing hole below the rear window, is it not possible to route the wires so they come from inside the trunk area to the trunk lid and use a plastic loom to keep them all together so there would not be so much tension on the harness, this would allow you to splice in extra length and it would just hang down in the trunk, just a thought
 
#60 · (Edited)
I suppose it would be technically feasible as long as the harness is properly supported and protected, and the passthroughs in the trunk lid and body are sealed. However, I'm a stickler for making repairs and modifications that look stock and, more importantly, don't introduce potential problems. The factory harness routing puts all of the wire behind the carpeted panel on the right side of the trunk. Objects in the trunk would snag an exposed harness and damage it, and its appearance would also turn away potential buyers who know what the stock harness routing should look like. Some might consider it a hack job and look for another car.

Running a new harness along the same route as the stock harness, with more durable wire, would be the better choice from aesthetic and functional standpoints.
 
Top