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Audi: 1999 A4 rear defroster question

  1. #1
    Chris
    Guest

    1999 A4 rear defroster question

    OK, after another frosty morning, I decided to tackle my broken rear
    defroster. There's power at the fuse panel and the yellow indicator
    comes on when I press the defrost button. So I popped off the C pillar
    trim and see a strange translucent blue box. On one end is a white
    incoming power (I'm assuming it's power) lead and a black antenna lead
    (with a little black pigtail going to one of the defrost element tabs).
    On the other end of this box is a black and red lead. The box itself is
    grounded to the body with 2 sheet metal screws.


    black (to defrost tab #1)----\ ---defrost tab #2
    \ |------------------|
    black antenna lead--------------| translucent blue |--------red wire
    white lead----------------------| box |
    |__________________|--------black wire



    The other tab for the defrost element is missing. Am I correct in
    assuming the black lead is ground and the red lead goes to the missing
    defrost element tab?

    Any suggestions would be greatly appreciated.

    Cheers,


  2. #2
    Clanger
    Guest

    Re: 1999 A4 rear defroster question


    "Chris Mauritz" <net> wrote in message
    news:Oz2Ib.28789$srv.hcvlny.cv.net... 

    following my heated wing mirror saga and wire tracking I came to the
    conclusion that there must be a relay aft of the cars main wiring, that
    controls the rear screen heater element. (1997/98 A4 UK model)

    what you describe, could this be a relay (the relay in question)

    white input = 12v 10A
    red input = 12v signal low power 3/5A (relay coil)
    black = radio antenna (top 3 wires of heater element)

    as for the red and black wires on output which looks the thicker.....this
    should be the heater element at 10/15A rating. The heater fuse in the fuse
    box being 10A

    one of these is probably ground for the relay coil and the other (thicker)
    power to the screen element

    only thing is I am not sure why radio antenna would go through this junction

    clanger



  3. #3
    Romy
    Guest

    Re: 1999 A4 rear defroster question


    "Clanger" <freeserve.co.uk> wrote in message
    news:bsrk14$l51$svr.pol.co.uk... 
    junction 

    Clanger is right. I haven't checked yet, but there must be some sort of
    timer relay for the rear defroster, it might even be built-in, or right
    behind the switch.


    Romy



  4. #4
    Clanger
    Guest

    Re: 1999 A4 rear defroster question


    "Chris Mauritz" <net> wrote in message
    news:Oz2Ib.28789$srv.hcvlny.cv.net... 

    I am not clear on the C pillar......do you mean the rear quarter pillar near
    back window.

    clanger



  5. #5
    TonyJ
    Guest

    Re: 1999 A4 rear defroster question

    The rear in-window AM antenna is AMPed in C pillar. Not sure but the
    defrost might be in the same component but seems unlikely.


    Clanger wrote: 



 

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