B7 to B6 Cabriolet Tail Light Retrofit?

Discussion in 'B6 platform' started by Chapunki, Aug 13, 2008.

  1. Chapunki New Member

  2. Advertisement

    • Premium Supporter

    PetrolDave Super Moderator

    Don't know about the cabriolet but the saloon and Avant rear tail lights are a very different shape between the B6 and B7, e.g. in the B6 the rear fog lights are in the main section but in the B7 they are in the section on the boot lid/tailgate.
    • Premium Supporter

    AudiA4B6US Super Moderator

    • Premium Supporter

    PetrolDave Super Moderator

    Just one thing worries me about that adapter kit.

    On the Kufatec website it says:

    • No alarm through passenger information system (cluster) regarding to an defective rear light.
    Does this mean that the rear bulb failure warning system will be disabled?
    • Premium Supporter

    AudiA4B6US Super Moderator

    No, the adapter contains a resistor to prevent the DIS from detecting a defective bulb because the new lights have only one rear light (on the other side is the fog light).
  3. Chapunki New Member

    Great, thank you guys, I knew I would need some sort of adapter harness.

    Went down to the dealership this morning and ordered a set, just have to get the adapter now. :D
  4. Daniel New Member

    Just did the upgrade and I am getting the infamous Bulb warning telling me that the left Rear Fog is bad...
    All lights work.. the worst part is that it does it randomly..
    Could it be the adapter?
    The lights look awesome though! :)
  5. wmccann New Member


    I did this and have the same problem, it is driving me crazy, I have tried everything. Same light - Rear Fog - thinking of trying a second resistor to increase the resistance.

    If you still have your old lights can you take a look and see what the wattage of the fog light was? (and was there a second one/resistor in the other light?


  6. urbun New Member

    Can you summarise what parts requirted to do job ?

    I have 2004 S4 Cabriolet and would like to upgrade rear lights too.
    Do you have a parts / price list I can work from ?
    Did you resolve the fault message displayed ?
  7. wmccann New Member

    I can't seem to resolve this issue - it is driving me nuts,

    I have tried increasing the resistance, decreasing it, replacing the wire, wiring directly and no luch same random "rear fog light bulb" warning.

    Anyone help??

    • Premium Supporter

    PetrolDave Super Moderator

    What value resistor are you using? It needs to "simulate" a 21W bulb to the bulb failure system - which means a resistance of 6.8 ohms with a power rating of (surprise!) 20W.
  8. wmccann New Member

    Thanks PetrolDave, tried that, Tried using a 21w bulb (no resistor), I have tried 3 power supply units and all to no avail, same issue.


    1) radomly shows rear fog light failure in the DIS on startup
    2) Always shows rear fog light bulb failure when I switch it on
    3) when swtiched on the fog light flashes

    could it have something to do with the earth connection I use (makes no sense but at this point it is the only thing i can think of!!!)

    Tests done (unless otherwise stated using a 21w bulb):

    1) Wired directly using rear light
    2) Wired using short cable from power supply unit to earth under dash
    3) Wired with second 21w bulb in parallel - still flashes
    4) Wired with second 21w bulb in series - still flashes
    5) wired with a 22ohm resistor only (no bulb)
    6) wired with a 7ohm resistor - 10w - no bulb
    7) wired with 2*22ohm and 1*7ohm 10w resistor in series - no bulb
    8) wired as 6 with a 21w bulb in parallel
    9) wired as 7 with a 21w bulb in parallel
    10) 1, 3,4,5,6,7,8,9 with a new cable from the power supply unit to the rear of car.

    All failed. Does anyone know what resistance the power supply unit is expecting?


    • Premium Supporter

    PetrolDave Super Moderator

    6.8 ohms - as already posted. Trust me - I'm an electronics engineer who has worked in the car industry...

    Those are classic symptoms of the bulb failure warning not seeing the resistance it's expecting. It does a low current sense at ignition on, a full sense when you turn the light on and if it senses TOO MUCH current is being drawn it protects the drive circuitry by turning it on and off - the flashing you are seeing.

    So that implies that there is TOO LITTLE resistance between the fog light output of the control module and ground.

    IIRC the B6 had 1 fog light (at least all mine did) and the B7 has 2 - so maybe you need a B7 version of the bulb control module?
  9. wmccann New Member

    Thanks for that,

    As far as I can work out the A4 B6 Cab had one 21w rear fog light. So I have no idea why 3 different power modules show the same symptoms.

    I have decided to get a 21w 40ohm potentiometer (actually for an amp) to see what resistance the power supply is expecting. Once I have worked this out I will calculate the extra resistance required.

    BTW, I was not questioning the use of 6.8ohms to simulate a 21w bulb, what I was actually asking is what resistance the power supply was expecting to see!

    Anyway will let you and anyone else with this issue know when I have my results (will take a week or so to get the potentiometer imported).

  10. wmccann New Member

    All is well again

    Hi All,

    Just an update, while trying to get my retrofitted auto lights to work (I did a low to highline conversion first) I found some very odd behaviour when I switched on the light sensor.

    Anyway to cut a long story short eventually traced the issue to a miswiring - I had put in a swtiched power supply to pin 1 on the light switch - this is connected to pin 18 on the power supply and so caused odd issues.

    Once I cut this cable, my auto lights, coming home lights etc worked and as an added benefit so too did the fog light.

    So seems that the unit does not like +12v on pin 18. "the dreaded fog light" warning issue is not an issue for me, just a bad cable.

    Anyway all happy now, thanks Petroldave for your help in this.


  11. TeknikL New Member

    retrofit kit

    the link is dead, where can I get the wiring kit?

  12. wmccann New Member


  13. Topjoe New Member

    I have a B6 S4 Cab and want to upgrade the tail lamps assembly as well. Can someone provide a parts list and instruction guide? The lights are about $162 each? About right? Will you need the new wiring harness? For the upgrade do you go with 2007 Lights to fit a 2005 car?

Share Audi Forum with friends