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Rear Light Cluster Bulbs

imported_ChristianF Mar 10, 2005

  1. Does anyone know what these consist of, namely the brake lights, are they dual filament stop/tail or are these two seperate bulbs one for stop and one for tail.

    without taking the cluster out, it looks like there is a tail light on its own and a stop/tail light seperate. is this right?
  2. mikeA2B

    mikeA2B Member

    Hi the tail lights are a little odd on the B6 A4 as I found out.

    The stop / tail is a single filament bulb (Like an indicator bulb but with an off-set contact in the cluster / bulb socket) located to the far end (closest to corner of car) of the cluster, and then a second side light bulb next to the stop / tail.

    When replacing the stop / tail bulb you can use a standard indicator bulb but you will have to carefully tweak the bulb cluster contact prong so it sits in the middle (have a look and you will see)


  3. so there are 4 single filament bulbs in the stop/tail lamp then?
    2 for stop and 2 for tail?
  4. a4sline

    a4sline Member

    The stop and tail bulbs are conventional 21/5W offset pin bulbs , however the single filament isn't used. Because the wiring is multiplexed, when the side lights are switched on the 21w filament is duty cycled from the J519 control unit, ie lower voltage(approx 4volt), then when the brake pedal is pressed J519 gives the 21w filament the full 12volt to get maximum brightness.
    This is why you see a lot of A4s with 1 or no brake lights, because the bulbs are pulsed they last a shorter time because they are being switched on and off by the control unit !!
    Little tip.......
    If you drive a 1.9tdi and the glow plug light stays lit...check that all brake lights are working, if not the diesal control unit checks it and puts the light on.
    Hope this helps and doesn't confuse too much
    Multiplexed wiring.... Lurvly. /ubbthreads/images/graemlins/woohoo.gif
  5. a4sline

    a4sline Member

    It sounds like the J519 control unit is playing games, as obviously the wiring , bulb holder and bulbs are ok and it's only 519 that has any bearing on the lights.
  6. Bet its not, there are 2 bulbs in the rear cluster for tail, inner one and outer one, the inner one has gone, its a 5w bayonet cap.

    I had same thing happen.
  7. Ah! Will investigate further!

    Advice much appreciated..!!!

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