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Thread: Fuse 58 Blowing

  1. #1
    Join Date
    Jun 2019
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    Glasgow
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    My Cars
    BMW e39 540i

    Fuse 58 Blowing

    Hi,

    I've seen a few posts with similar sounding problems, but not exactly the same, plus I've been searching all over Google without finding anything.

    My car is a 2002 e39 540i and has the widescreen sat nav radio with cassette player behind the main unit.

    The problem I've been having is Fuse 58 in the boot keeps blowing, stopping the radio from working. Nothing else appears to be affected (i.e. the computer and display still work), but the little orange light for the radio doesn't come on and pressing the volume knob to switch the radio on has no effect. This is a recent issue - it did blow once a few months' ago, but replacing the fuse at that time fixed the problem. It's only recently that the fuse has been blowing straight after getting replaced.

    I've tried replacing the fuse and it usually blows instantly when turning the key back to position 2.

    Have also done a visual check of wiring around the fuse box in the boot and it all looks ok (without trying to take it all apart).

    Have also tried taking the radio unit out of the dash and checked the wires behind it (again.. all looked as good as new.. no dampness, frayed wires etc).

    Interestingly, while messing around unplugging and plugging back in the radio, it did actually start working again, but after putting it all back together again and starting driving, the fuse blew again after a couple of mins.

    So.. in summary.. the radio doesn't appear to be broken, as it works sometimes, until the fuse blows again.

    I can't seem to find any info anywhere about where the wiring actually goes (i.e. where it runs from the dash to the boot) and/or how you would access it to see if there are any obvious short circuits.

    Not sure what to do as no point buying a new radio if the problem is in the wiring, and I don't really know enough about it to start taking the car apart to look for wiring issues!

    Fuse 58 is just marked as 'Radio' in the fuse box, but so are another 4 fuses.. does anyone know exactly what fuse 58 does and what could affect it? From Googling, some have suggested it could be linked to the phone too? It's the 10A one.

    Have had a few different cars over the years (E36 323, E46 330i, E39 535i, E46 330Ci) but this is the first time I have experienced this issue.

    Appreciate any suggestions!

    Cheers,
    D

  2. #2
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
    Join Date
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    Location
    Sundance Mesa, NM
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    00 540/6, '16 Highlander
    Welcome to the forum deeko.
    F58 should go to the Unloader relay K3, terminal R.
    It's probably the 2nd relay from the front on the left side of the relay/fuse holder above the battery.
    The Unloader relay powered a few things for a short period of time after you turn the key off.
    Last edited by JimLev; 06-17-2019 at 01:26 PM.

  3. #3
    Join Date
    Jun 2019
    Location
    Glasgow
    Posts
    2
    My Cars
    BMW e39 540i
    Thanks JimLev - do you know if relays are problematic - i.e. could it be an issue with the relay that is causing the fuse to blow, or is it more likely to be an issue with one of the things that it is powering?

  4. #4
    Join Date
    Jan 2016
    Location
    Ca
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    My Cars
    2001 525it
    I would check out the ignition switch too, they can start to to strange things I replace mine recently as preventive maintance

  5. #5
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    Sundance Mesa, NM
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    00 540/6, '16 Highlander
    Deeko, do you have an amplifier in the boot or just a radio with built in amp in the dash?
    I'd try unplugging the radio (and amp in the boot if you have one) then replace the fuse and see if it blows.
    That will tell you if it's the radio or amp or the wiring.
    The wire that leaves K3 is the switched 12 volts, it should be violet/white.

    Update:
    K3 fuse gets power directly from F106. F106 should always be hot, so that should rule out the ignition switch as the issue. F106 is in the fuse block just above the battery and feeds F56 to F59.
    From the K3 relay (depending on options) the switched 12 volts goes to:
    NAV
    Radio
    On Board Monitor
    Telephone.
    Last edited by JimLev; 06-19-2019 at 12:28 PM.

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