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Thread: Interior Lights.....beating dead horse.....a mystery.

  1. #1
    Registered User Aronis's Avatar
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    Interior Lights.....beating dead horse.....a mystery.

    Here is where I am at with this issue.

    I have confirmed the dimmer switch Rheostat functions properly, so it is not the mechanical switch.

    Proof:
    1. Measure with ohm meter, range is the same for both the switches I have.
    2. The lights in the instrument cluster, radio and A/C display panels all dim properly.
    3. Backlight switches in Radio function properly.

    The lights which do not light up at all....all the rest of the switch backlights. A/C control module, hazard flasher, head light switch, fog light switch, heated seat knobs, cigarette lighter backlights, head liner switches for dome and map lights, rear also, etc.

    Here is the wire diagram in question.

    Click image for larger version. 

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    Note: TO RADIO!

    If this is the wire which sends current to all those bulbs listed AND to the Radio to control it's dimming then WTF? I cannot find another wire going to the radio that controls it's dimming, but either there is another circuit doing this or there is a common wire in the wire harness A19 that is broken going to all the rest of the lights, but not to the radio?

    But that does not explain the short that takes out the fuse in the instrument cluster.

    When I plugged in the new instrument cluster, those lights still did not light, but the fuse 15 no longer blew and the volt meter worked. I did not yet go through installing the new instrument cluster for fear that what ever took out the lights also will burn out that new one.

    I don't think there is any other control module between these wires. See the diagram to L120 and L121 (storage compartment illumination and cub holder illumination) which go to bulb and to ground.

    Thoughts?

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  2. #2
    Registered User Aronis's Avatar
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    New finding, my side mirrors do not work.....just the folding-back circuit works.

    Looking at diagram for that......guess what fuse goes to the mirror control unit? Fuse 15. LOL....same one that goes to the instrument cluster....

    Now I am sorry I did not replace the fuse when I had the friggen drivers side door all unplugged. If there ends up being a short there in the mirror control wires that could explain the whole thing.

    I am trying to trace the wires to the mirrors from the control unit to see where power goes to first...through the control unit to the mirror or to the mirror then back to the control unit - which is what I'd bet since this would protect the control unit if there was a short - i.e. control it by switching to ground.

    Next step....take the friggen dash apart again, and unplug the drivers side door again, replace the fuse and see what happens.



    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  3. #3
    Registered User Aronis's Avatar
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    I unplugged drivers side door wire harness (four connectors and a pain in the ass), but fuse 15 still blew, unplugged passenger side door, ohm meter reads 18 ohms at fuse 15 and fuse does not blow. Points to fault in passenger side door perhaps. But display still says "Fuse" and Voltmeter still not working.

    So both mirrors are now unplugged, perhaps there is a fault there somewhere. I cannot really see the interior lights (day time) so I am going to take a peak at night to see. Still does not explain the instrument cluster fault unless that internal circuit is fried by exposure to the prior short. May be time to put the transplant cluster back in to just see......

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  4. #4
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    See here:

    https://www.audiworld.com/forums/a6-...oblem-1726146/

    Have you thoroughly checked the wiring in the body harness?

    You need to remove the driver's seat .
    2012 Q7 TDI S-Line - 2010 GTI - 2007 A3 3.2 S-Line - 2003 RS6
    2001 Honda S2000 - 1977 Honda CBR 750-F2 - 1965 GMC 1500 WideSide

  5. #5
    Registered User Aronis's Avatar
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    Remove the seat! ARRRRRGGGGGGHHHHH


    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  6. #6
    Registered User ben916's Avatar
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    Quote Originally Posted by Aronis View Post
    Remove the seat! ARRRRRGGGGGGHHHHH


    Mike
    careful of the airbag...
    SOLD - 03 RS6 Avus (905355)
    Current - 03 Toyota Tacoma 4x4 double cab - the YETI, lifted, winched, snorkeled, lockered, skidded, geared

  7. #7
    Registered User Aronis's Avatar
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    Quote Originally Posted by ben916 View Post
    careful of the airbag...
    LOL....they are 15 years old and ready to blow at any minute.

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

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