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Audi S4 Rear LED

Discussion in 'A4/S4 forum(B5 Chassis)' started by Nez, Aug 14, 2010.

  1. Nez
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    Nez Member

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    Hi guys just need abit of help here with my LED rear lights I just fitted them and now I get a faulty light on dash saying my rear break lights is not working and I checked it and its working fine, is this something do with the LED?
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  2. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    yep. The bulb monitor box calculates the current drawn by the bulbs, and if its too low brings on the warning.

    LED's draw very little current, hence it thinks the bulbs have blown.

    You can get ballast resistors, or alternatively, bypass the bulb monitor for that circuit.
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  3. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    I went for the resistors so if heven forbid the lights went out the warning would still work.

    You will need 2 per side, one for the side light circuit and one for the brake light circuit per side
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  4. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    they wouldnt still work though :p

    Resistors would continue showing a load, and the box would be none-the-wiser!
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  5. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    it does, so ner

    I popped a fuse en route to AITP and the dis had a fit, i spose it could have been due to the front ones going off, now i think about it......

    "runs and hides"
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  6. Jonion
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    Jonion Member

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    They should still work.
    The resistors show a load similar to a bulb. If a bulb/LED blows it will show no current flow (open circuit) and put the warning light on.
    The reason the warning light comes on with the LEDs is the low load they have so it probably won't detect a shorted bulb, which are rare anyway.
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  7. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Resistors are in parallel to the LED's though, so when the LED's blow the resistor will continue pretending to be a bulb, and the warning will stay off.

    Fuse comes after the load box, so the system sees signal in and no current draw, and brings on the warning.
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  8. Jonion
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    Jonion Member

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    Ah, yes running them in parallel will cause a problem then.
    I run mine in series.. not on the Audi though.
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  9. Nez
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    Nez Member

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    Thanks :) Is there any DIY in the forum to show me how to do this :(
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  10. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Which bit?
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  11. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Stick to the ballast resistors, Its a pretty easy DIY compared with ripping your central electrics board apart!
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  12. Nez
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    Nez Member

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    The resistors bits :)
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  13. Nez
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    Nez Member

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    Where do I put the resistors I mean where in the light do I need to install the resistors.
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  14. jcb
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    jcb Active Member

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    anywhere in series arent they?
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  15. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Series will reduce the voltage going to the LED's so not ideal.

    You want to mount the wires between the live and earth for the brake bulbs (ie in parallel), and then mount the resistors somewhere.

    The resistors get quite hot in operation though, so you'll want to mount them on a piece of metal or similar.
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  16. Nez
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    Nez Member

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    Cool thanks for the reply is this what I need?

    http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=320304369615&ssPageName=STRK:MEWAX:IT
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  17. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Yep, 4 of those bad boys
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  18. Nez
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    Nez Member

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    Cool thanks will order them tonight :) thanks for all replies guys :) by the way Byzan is possible you can send me the picture of your rear LCD lights how you connected you one :)
    Last edited: Aug 17, 2010
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  19. Nez
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    Nez Member

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    Hi guys again I need help I get the resistors today and I connected like this (+wire --- resistor ---+wire = break light) and I still have the faulty light on dash :( looks like I done something wrong here :(
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  20. 27litres
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    27litres Love My Quattro

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    Sounds like you did it wrong...
    find the +ve & -ve wires for the brake light (on the loom/plug, not in the LED circuit board). tap into both wires and connect the resistor to your wire taps. That will simulate the load across that circuit...

    Edit: Should be the plain green and plain black wires either from the top of the taillight (where the LED circuit board is), or at the plug - provided you have the same style of LED taillights to me!
    Last edited: Aug 24, 2010
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  21. Nez
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    Nez Member

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    Thanks for the reply I try this and see what happens :)
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  22. 27litres
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    27litres Love My Quattro

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    Nez,
    How'd it go?
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