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Thread: Trunk Lights won't go off! Switch works.

  1. #1
    Join Date
    Jun 2008
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    SF Bay Area
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    Supercharged 850ci

    Trunk Lights won't go off! Switch works.

    Pushing the switch next to the trunk latch only dims the trunk lights somewhat but doesn't shut them off.
    Battery get's drained overnight!
    Change the switch to a known good one, same situation. So I removed all 3 trunk light bulbs for now.
    On the other 8 pushing the switch will turn off the lights... any ideas why this circuit would not work?

  2. #2
    Join Date
    Dec 2006
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    warwick RI
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    E30/E32/F25
    Remove switch completely and see if lights turn off, If it doesn’t you probably have a chafed wire. the switch uses the body as a ground so if a wire gets chafed or broken it will illuminate your light when it comes in contact with the body. Check wire from switch and check trunk hinge area for broken wires. Hope this helps !
    Me E30 87/ 325i + F25 12/ M-Sport + E32 94/ 740i

    G/F’s E34 92/ 525iT + F48 18/ X1

  3. #3
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    Hello, removing the switch only dimmed the lights like pressing it. I will check for chafed wires!

  4. #4
    Join Date
    Aug 2007
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    San Ramon, CA
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    850Ci, M5, Model-S P85D
    Quote Originally Posted by dragon850 View Post
    Hello, removing the switch only dimmed the lights like pressing it. I will check for chafed wires!
    Unfortunately, the trunk lid wire looms are problematic at best, horrible at worst and not easy to fix if you want a quality repair.
    My 8 is a 1997 and a 80k mile Garage Queen and my car had problems with a tail and licence plate bulbs on the trunk lid several years ago.
    Several of the individual wires on both sides of the trunk hinges (in the flexible sleeving section) were broken from over flexing.
    The wire flexing (service loop) from opening the trunk is not designed for long life and you can anticipate every 8 has some wire fatigue (a few broken strands) or complete wire failures (all strands are broken to include the insulation) in the trunk wiring loom.
    It is how the wire loom twists at both trunk hinges what breaks the wires.
    IMHO, The wire loom can be adjusted to reduce the tight flexing but no matter what the OE wire loom fatiguing cannot be eliminated due to the hinge and wire routing design.
    The best option would be to replace the vinyl insulation 7-strand wire by splicing in silicone high strand count wire for the larger gauge wires that can better accommodate the required flexing.

    See attached image:
    Attached Images Attached Images

  5. #5
    Join Date
    Sep 2008
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    Santa Barbara
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    91 Dinan860 & 91 850 6sp
    was this car hacked up with an aftermarket alarm?
    I ask, because that is in the circuit too... and if grounded (badly, it seems), would cause the lights to glow
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  6. #6
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    Move/wiggle the trunk wiring harnesses at the hinges to see if the trunk lights flickers!!

  7. #7
    Join Date
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    It does have an aftermarket alarm installed. I will try wiggling the wires to see if lights flicker.
    Car has 75k miles on it.

  8. #8
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    I doubt it's the alarm as it's only sharing your parking lights.

  9. #9
    Join Date
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    Quote Originally Posted by 8eights View Post
    I doubt it's the alarm as it's only sharing your parking lights.
    not entirely correct... even the factory setup has a wire that goes to the ground side of that circuit back there - it monitors the trunk switch
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  10. #10
    Join Date
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    6.5 second 69 Camaro
    I was speaking of the aftermarket alarm as no wiring is needed pass the steering wheel, Usually doesn't tap into lights that fade to the off position. That light half off in Dragons trunk is a first for me.

  11. #11
    Join Date
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    99 840ci Sport Indv
    Yes, the Body Electronics Module and the DWA is connected to the 'ground' side of the bulbs before the boot switch - but, more likely the boot-hinge wiring has come a cropper:

    https://www.meeknet.co.uk/e31/e31_91.pdf#page=280




    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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