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VagCom Disabling bulb alarm?

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Anorien, Jan 28, 2006.

  1. Anorien

    Anorien New Member

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    Anyone know if it's possible to disable the bulb sensor thingy on a 2002 A4?

    Im looking at fitting a HID set to my high beam but the car cuts the current to the light as soon as it's turned on and reports a failed bulb.

    Turning the high beam on and off a few times seems to fix the problem but this is obviously not ideal.

    Anyone else come across this when changing bulbs?
     
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  3. peteA3tdi

    peteA3tdi Member

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    when you say high beam do you mean main beam for flashing or very dark roads or do you mean dip beam normal night time lights
     
  4. Anorien

    Anorien New Member

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    The high beam (flashing / dark roads etc) ....

    I've converted the main (dipped driving) beam to HID and I would like to do the same to the high beam (full / flash).

    Trouble is when changed to a HID set the High / Full beam will not stay on ... The high beam will come on and then turn off again and the car reports a failed bulb.

    I can fix the light by using a couple of relays so that it'll stay on as required but the car still reports a failed bulb.

    All I need to do is somehow disable the bulb warning for the front lights (which to me seems stupid because it's pretty obvious if your headlights aren't working !!)
     
  5. dstech

    dstech Member

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    If the bulb goes out then the electrical control module is turning off the relay and then putting the bulb out indicator in the dash.

    There isn't any way to get rid of this warning.

    Try changing your coding to the electrical control module to a different country. Not sure why this would work but I guess it's worth a try.

    What system did you have stock? Xenons or Halogens? Bi-Xenons?
     
  6. timps

    timps Shakersville

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    Not done this myself

    But the warning is triggered buy circuit resistance & any variation from a set figure triggers the warning lamp.

    So it makes sense that if you match the original resistance the warning will go out, so this might work.

    Check the resistance of the original bulbs you have replaced then check the resistance of the new bulbs.

    (using a mutimeter)

    1 if the new bulb is lower include a load resistor with one end connected to the feed of the bulb and the other to ground.

    2 If the new bulb is a higher resistance then use a relay and a load resistor with one end connected to the trigger feed of the relay and the other to ground.

    If the total Ohms matches the original bulbs this relay will now have the same figure as your original bulbs and not cause a fault & will supply current to the new bulb & keep it on.

    Which ever way as long as the figures match the original bulbs the bulb indicator will go out.

    It might work

    Then again………
     
  7. firestorm

    firestorm Member

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    Anorien,
    I've done exactly what you have described, it took me a while to get working, but here goes :

    B6 A4 TDI Avant, 2002

    aftermarket HID by KDG

    low beam works a treat
    high beam cuts out as the bulb warms up and the bulb blown alarm sounds.
    Bulb alarm sounds when ignition II is activated.

    I tried wiring in a 22R, 25W resistor in parallel with the input to the ballast to simulate a normal halogen bulb better, but it still cuts out. Bulb alarm sounds when ignition II is activated.

    Sames as above, but with two 22R resistors in parallel, made no difference. Bulb alarm sounds when ignition II is activated.

    In both cases the power is cut off to the ballast. However, if there is no ballast connected at all, the Bulb alarm still sounds when ignition II is activated, but there is +12v !

    So I used the original high beam bulb feed to activate a relay which in turn powered the ballast from the battery.

    This worked a treat for me. Except the bulb alarm sounds when ignition II is activated and when high beam is switched on.

    I wired in the 22R, 25W resistor in parallel with the input to the ballast to simulate a normal halogen bulb better, but it still cuts out. Bulb alarm sounds when ignition II is activated.

    Sames as above, but with two 22R resistors in parallel everything was ok. I am speculating a 15R 25W would do ok. I've yet to order a pair, as the lights are working now, but the bulb alarrm is annoying, so I'll do it soon.

    This has been my experience, of course ymmv.

    Also have you found any issues with radio reception ?
     
  8. Lynas

    Lynas Member

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  9. firestorm

    firestorm Member

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    I don't recommend a 3R3 resistor. Worst case, it will dissipate over 51W. The resistor in that kit looks like its unlikely to cope with more than 10W.

    I am using 25W resistors ... with the values I have chosen (11R), just a tad over 15W is dissipated.
     
  10. timps

    timps Shakersville

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    [ QUOTE ]
    I don't recommend a 3R3 resistor. Worst case, it will dissipate over 51W. The resistor in that kit looks like its unlikely to cope with more than 10W.

    [/ QUOTE ]

    It does not need to cope with anything that large once you switch the lights on the relay breaks contact so it only has to cope with the check from the electrical control module when the lights are off hence the 1.5 amp or 2.5 amp fuse depending where you look.

    If you add a second Relay in the circuit shown on that link with an appropriate resistor after the relay coil in a loop to mimic the bulb you have replaced but do not connect the ballast directly to this loop this should keep the bulb warning lights off.

    To power the ballast take a feed off the battery and run it through this second Relay and ground the ballast directly to the chassis.

    That’s what I would try any way
     
  11. firestorm

    firestorm Member

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    timps,
    I've misunderstood the wiring of the relay & resistor - you are saying that the relay is wired up, so that the resistor is normally in circuit with no main power and that with power the R is out of circuit. Therefore the R can be very low value and low power, as it is taken out of circuit when power is applied.

    I have wired it so that the relay swtches the ballast on and off. The R I have is in circuit all the time.

    I will try the method suggested as it seems a lot more efficient and elegant - assuming it is sufficient to full the bulb monitor system,
     
  12. timps

    timps Shakersville

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    [ QUOTE ]

    I have wired it so that the relay swtches the ballast on and off. The R I have is in circuit all the time.


    [/ QUOTE ]

    If you run this in a loop + to - from the bulb feed with a resistor in series to mimic one bulb then do the same on the other side (no relay needed) as long as the resistor matches the bulb I cannot see why this does not work.

    Audi with dis tells you which side is blown on all the other bulbs (not sure on main beam) but could this be your problem if there is no resistor on the other side?
     

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