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Thread: Rear Fuse Box Wiring Nightmare - no windows/door locks/wipers/auto interior lights

  1. #1
    Join Date
    Jul 2012
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    South Yarmouth MA
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    11/87 735i & 735il P/C

    Unhappy Rear Fuse Box Wiring Nightmare - no windows/door locks/wipers/auto interior lights

    Hello all,

    It's mid-July now, and that means hot temps. I'm getting increasingly frustrated by my lack of power windows. So here's the story...

    I bought this car after it sat for 10+ years. I think I now know why it sat so long... somebody tried to install an aftermarket alarm. I say 'tried' because it appears that they gave up mid-way through the installation. There was a new alarm horn put near the alternator with 'Predator Alarms' on it, and a little red light professionally installed next to the window switches.

    Whoever attempted the install absolutely butchered the wiring under the rear seat and carpets. There are a myriad of wires capped off seemingly at random. As such, the windows, locks, and auto interior lighting don't work. The wipers only work on high and won't 'park' themselves.

    IMG-2757.jpg IMG-2758.jpg IMG-2887.jpg IMG-2891.jpg IMG-2890.jpg

    Some thing's I've already done:

    -swapped in known-working RM & GM from 1988 735il parts car; no change
    -checked fusable links and tried jumpering - voltage tested okay; no change
    -triple-checked all fuses
    -measured voltage at female pins for the GM - only the top (closest towards center of car) left-most one had any power. All others 0 volts.
    -measured voltage at the blade fuses under the rear seat - all tested 12v.
    -tracing the wires from left rear door - some seemed to be capped off?
    -began cutting out the entire rear fuse box from the parts car to swap it in... gave up upon realizing there are multiple wires of the same colors and it will be impossible to match them all up properly



    I'm starting to think I may have to surrender to a really good BMW specialist who already knows this wiring system, because I'm getting very demoralized trying to figure out the hundreds of wires with no clue where to start...


    Does anyone have any suggestions or is this beyond our collective expertise? Are there any trusted mechanics in Massachusetts who know the e32 electrical system really well?
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  2. #2
    Join Date
    May 2018
    Location
    UK
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    19
    My Cars
    1994 740
    I would seriously consider buying a loom from a junk yard.

  3. #3
    Join Date
    Jul 2012
    Location
    South Yarmouth MA
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    550
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    11/87 735i & 735il P/C
    I could take the loom out of my parts car, but I'm not sure I'm up to the task of retrofitting it in... seems like the rear fuse box has wires running everywhere in the car
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  4. #4
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    For that ones needs someone with electric knowledge, that is indeed a nightmare. Here some pics when we removed all the wire looms inside an 10/88 750iL which we parted http://www.bimmerboard.com/forums/posts/270025/
    Shogun tricks and tips for the E32 series are HERE!

  5. #5
    Join Date
    Jul 2012
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    South Yarmouth MA
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    550
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    11/87 735i & 735il P/C
    Thank you Shogun

    I should clarify specifically what I'm hoping someone on this board knows: the colors/locations of the wires that control the windows. I'm hoping I can trace those and fix any problems I find easier than replacing the whole wiring loom
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  6. #6
    Join Date
    Jan 2005
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    Japan
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    11/88 E32 750iL+98 E36M3
    this will help, start from the GM, here I posted the pinout of all pins of the GM, and at the pins you can see the cable colors
    Central body electronics ZKE = GM pinout http://www.bimmerboard.com/forums/posts/1229510
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
    Join Date
    Jul 2012
    Location
    South Yarmouth MA
    Posts
    550
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    11/87 735i & 735il P/C
    Thank you!! That is exactly what I needed

    I will report back on any progress I make
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  8. #8
    Join Date
    Jul 2012
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    South Yarmouth MA
    Posts
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    My Cars
    11/87 735i & 735il P/C
    Can anyone identify this relay? Some of the wires from the 26-pin connector that controls the windows go into this module/relay.

    Mystery Module 1.jpg Mystery Module 2.jpg Mystery Module 3.jpg


    Also interesting to note the window switches do not light up when the headlights are on, but the sunroof switch does light up, so it must be getting power. Any thoughts on what this means?


    UPDATE: googled the p/n and found it's a wiper pressure control relay. Why would that have anything to do with the windows? I'm lost.
    Last edited by CamE32; 06-15-2018 at 11:33 AM.
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

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