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Thread: Fuse #5 keeps blowing...

  1. #1

    Default Fuse #5 keeps blowing...

    Hello all!

    I have a 1991 535i 5-speed I call Sinbad.

    I am having a problem and could really use some help. If anybody here has ideas on my electrical problem, PLEASE post! I have the E34 Bentley manual, and the schematics are very nice... except I do not know the wire routing and don't want to tear up the entire car when it might be much easier to do a spot check somewhere.

    My fuse #5 keeps blowing whenever I turn the parking or headlights on. Once the fuse blows (or is removed completely, as it is now), I get the following symptoms:

    - Instrument illumination (console/dash lights) is out
    - Passenger side parking lights are out
    - Error message on OBC display that says "Parking Light +" and another error message

    Things I have already tried:
    - Have replaced the headlight switch (and fuse again) with no success
    - When headlight switch is in the Park or Headlight position, I measure 12.4 V across fuse 5 socket.
    - Disconnected some of the load (right front parking light, right rear parking light, interior light dimmer, LCM or lamp control module) and get same readings.
    - Disconnected headlight switch and jumping RED/BLUE coming into switch to GRY/YEL and still measure 12.4V. Jumped red/blue to GRY/BLK and still measure 12.4V.

    My questions:
    - Is there any more load that I am missing or needs disconnected? The GRY/BLK wire goes to the Interior Lights system, which seems pretty complex. If I have disconnected all the load, then I would want to trace GRY/YEL and GRY/BLK along a common path where they might both be severed and shorted to ground. My gut feeling tells me there might be more load on GRY/BLK that needs disconnected.
    - Anybody seen this before?
    - What are some common junction points for the GRY/BLK wire? Some I can disconnect and test to try and isolate the source of the problem.
    - Do I really have to remove the steering wheel and dash to dig deeper? I would like to be 80% sure the problem is in that area before that time consuming task. Trying to avoid any wild goose chases if possible.

    Any help is much appreciated! If you guys have some suggestions or tests, I can check it out. TIA!

  2. #2
    Join Date
    Jan 2004
    Posts
    1,342

    Default F5 also feeds License Plate lights, so it ...

    feeds a Gray/Brown wire, and a Gray/Brown/Yellow wire that run trough the Trunk Hinge Harness.

    Do a search under Hinge Harness and you will find plenty of information on this miserable bug on E34's.

    Javier

    Edit: An easy check is to remove LKM to verify if bug is related to Lamp circuits after LKM (like trunk hinge).
    Last edited by Javier; 08-19-2006 at 08:51 PM.

  3. #3

    Default

    LKM = lamp control module, right? I have removed that already and still getting a short.

    I also checked that hinge the other day by taking off the plastic covering and looking at the wires. They look great but I'll also do a search to get more description on what I am looking for.

    Thanks!

  4. #4
    Join Date
    Jul 2006
    Location
    Houston, Tx
    Posts
    592

    Default

    I'd start simple and look for a wire touching frame or body. My friend was fighting blown fuses for a month and when I found out his car was hit in the front, I discovered that his horn wires were crushed and exposed and arcing on the frame shorting his light circuit and bang... no horn or tail lights. Little electrical tape and the car's 15th or 16th fuse since I got there, and he has lights and a horn! Whodathunkit?

  5. #5

    Default

    removing the LMK, disconnecting right sidemarker bulb/connector, and disconnecting the rear right tail light, and did another measurement.

    Took DC voltage from the fuse 5 socket to Gray/yellow wire connector for the headlight switch (switch removed), and still read 12.4V across it. I suspect that GRY/YEL wire is grounding somewhere.

    Anybody know where this wire snakes around? Hopefully I don't have to take the car all apart but will do it if I have to. ugh.

  6. #6

    Default

    I think thats probably whats going on... just gotta find it! haha

  7. #7
    Join Date
    Jan 2004
    Posts
    1,342

    Default Gray/Yellow wire goes trough splice X245 to ...

    LKM pins 7, 27, and to rear and front right side markers. Splice X245 is in the front harness between the Light switch and the LKM, one wire in, four wires out. Gray/Yellow wire for the rear right marker, also goes trough connector X13 (21 pin white connector below driver's foot rest).

    Javier

    Edit: If you removed both right side markers and the LKM and still get continuity to ground on Light switch Gray/Yellow wire, no doubt you have a short to ground in the Gray/Yellow wire system coming out of Light Switch. You may select to replace all this wire system together running alternate cables (first unplug X13 below foot rest to discard a fault in the rear side marker cable itself, from X13 to the bulb).
    Last edited by Javier; 08-20-2006 at 07:29 AM.

  8. #8
    Join Date
    Jan 2004
    Posts
    1,342

    Default How did you detected the short after removing LKM? ...

    Put and blown a new fuse? To measure voltage across F5 and find 12V does not mean there is a short there until you are positively sure all load was removed.

    You can also test across F5 with a bulb light. If normal brilliance is achieved yes there should be a short. If dimmed, probably remaining load.

    Javier

  9. #9

    Default

    I do have a few more fuses... so I can try that.

    I have been measuring the same 12.4V across F5 both with and without the LKM. Whatever a bulb light can detect, a multimeter should be able to read as well, right? (I would expect a lower voltage to result in dim bulb light. Just working with what I have)

  10. #10

    Default

    So removing the driver side foot-rest (dead pedal, left of clutch, right?) and I will find X13. That will help a bunch, thanks!

    X245... which side of the firewall is that? Deciding to tear out the interior dash or if I need to take out the fuse box to find it.

    Thanks for the help! Much appreciated!

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