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LED side lights and canbus wiring - side lights on all the time

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by M7R, Oct 7, 2008.

  1. M7R
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    M7R Type Approval Engineer,

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    [Oct 7, 2008]
    I have managed to get rid of the crappy yellow bulbs with some nice white xenon bulbs and all is well, but the big left down was the yellow side light bulbs, so I had the brillaint idea of a pair of white LED ones, using 4 tiny LED bulbs, and they did look the dogs danglies! plus they were brighter and I hate not being seen as I do alot of night driving.

    the down side is the bulbs are permantly on, when the lights are turned off the LEDs glow dim on about 1/2 power. Is there anways I can fix this? im guessing I need a resistor of some sort inline?

    cheers

    Karl.
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  3. PetrolDave
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    PetrolDave Well-Known Member

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    [Oct 7, 2008]
    The LEDs are on all the time because the bulb failure check actually puts out enough voltage to turn the LEDs on.

    If you put the LEDs in series to stop them glowing then you'll get a bulb failure warning, so you'll need a parallel resistor to stop the warning.
    #2
  4. M7R
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    M7R Type Approval Engineer,

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    [Oct 7, 2008]
    cool, any idea what value of resistor is needed?
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  5. PetrolDave
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    PetrolDave Well-Known Member

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    [Oct 8, 2008]
    The sidelight bulb is 21W IIRC, and the LEDS will take only a fraction of that so you need a resistor that will draw say 15W - which means a resistor of about 10 ohms.
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  6. M7R
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    M7R Type Approval Engineer,

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    [Oct 8, 2008]
    side lights are 5w, so i guess ill assume the resistance from the leds can be egnored.
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  7. 1wheelonly
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    1wheelonly cabriolet VCDS Map User

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    [Oct 8, 2008]
    youll still need to resist them, i think i put 2k across mine to stop the faults, mine used to flash.
    #6
  8. Richardesty
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    Richardesty loves quattro

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    [Oct 10, 2008]
    Yeah - I also installed resistors, but also moved the position of the sidelights whilst I was at it....

    [​IMG]
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  9. M7R
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    [Oct 12, 2008]
    can anyone tell me for sure what resistor they used and exactly how they installed it? as I fitted a 2k ohm resistor accross mine today (crudely done by wedging it down the side of the side light bulbs but it did make a connection and it was out fo the car to see if it worked) and it wouldnt work, to start with one light was dimmer than the other only getting 10v, then the car chose to stop one light as it thought the bulb had blown! then after taking the battery off and back on I got it to work but they would come on, flicker a couple of times and then go out.

    now the fact they go out does that mean that theres too much resistance? i reeaaallyyy want my lights work as everything else is done now so these are really leffing the front of the car down,

    cheers

    Karl.
    #8
  10. PetrolDave
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    PetrolDave Well-Known Member

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    [Oct 13, 2008]
    Yes, you need a much lower value than 10K ohms.

    I've seen one person saying that 2k ohms worked for him on the sidelights. I'm surprised that high a value is OK, personally I'd expect a value below 100 ohms to be required.

    What you want is the combination of the LEDs and the resistor to take about half the current that a bulb would - that's usually enough to make the bulb failure system think everything is OK. If you assume the LEDs take nothing (an LED takes 20-50mA, a bulb takes 10-100 times that so is a fair simplification) then you can work out what value resistor you need -> R = V squared (i.e. 144) divided by (half the bulb power).So for a 5W bulb you want a resistor of about 30 ohms.
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  11. M7R
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    M7R Type Approval Engineer,

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    [Oct 14, 2008]
    brillaint, Ill see what we have at work, or failing that a trip to rs is in order. :rock:
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  12. M7R
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    M7R Type Approval Engineer,

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    [Oct 18, 2008]
    still I keep going.....

    I tried a 27 and the resistor over heated when the side lights were on started to smoke! this was a RS resistor from work.

    would I be better trying a 33 ohm resistor? ive seen on ebay that they do resistor for my problem and they are only 25ohm though, but do come with a big heatsink..
    #11
  13. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Oct 18, 2008]
    Better big heatsink than melted headlight or worse melted car, you need to get a few at different rating & try them & check the heat of them to make sure its not a danger to the car of course.
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  14. PetrolDave
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    PetrolDave Well-Known Member

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    [Oct 21, 2008]
    You not only need the correct resistance value you need the correct wattage rating of the resistor - sounds like you used to low a wattage rating...

    A 27 ohm resistor will dissipate about 6W, so you need a resistor of at least that and probably a 10W is the one to go for.
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  15. gtiller
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    gtiller Member

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    [Dec 28, 2008]
    Sorry to hijack a thread...

    I have an A6 now, and am in the process of finishing the S6 DRL mod.

    Currently, I am getting the bulb failure warning - so I need a resistor.

    As my LEDs replace a 55 watt lamp, I am trying to determine what size resistor I need, and whether i need to install in series or parallel.

    I have a couple of 2R7 50W resistors in the garage, and as they are set in a nice big heat sink, I would like to use them if possible... however, I think they might not be heavy enough.

    Any advice would be appreciated
    #14
  16. dgruidi
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    dgruidi New Member

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    [Jun 17, 2010]
    I bought some canbus warning bulb.And I put it into my car as test.It can work well.If you are looking for the canbus led.You can contact with you.I can help you find the manufactuerer. nordy@dgruidi.com
    #15
  17. doug.p
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    doug.p Getting There VCDS Map User

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    [Jun 19, 2010]
    i fitted all this to my car and have run it now for a few months, i did a how to with links to all the correct bits of kit at the cheapst prices i could find
    do a search for my how to thread
    :)
    #16
  18. ywledmsn
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    ywledmsn New Member

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    [Jun 27, 2010]
    Model: canbus T10-WG-8x3528SMD
    Led Quantity: 8 pc 3528 smd
    Lamp Socket: wedge(canbus led)
    Emitting Color: white, warm white, blue, green, red, yellow
    Available Voltage(V): DC12/24V
    Luminous intensity:white 65lm
    Average life time: ≥50, 000 hours

    BMW Canbus Led >T10 Series

    Super Bright 360-degree shine SMD (SMT) Festoon LED bulbs with built-in load resistors,specially designed for European vehicles such as Mercedes, Audi, Volkswagen, Porsche or BMW, etc.
    These OBC Error Free T10 Wedge LED bulbs will replace the stock 168, 194, 2825, 2821 or W5W bulbs.
    The length of this T10 LED bulb is approx 1.15 inches. Since this T10 LED bulb is slightly longer than the stock wedge tungsten bulb, so buyers must make sure the this T10 SMD LED bulb can fit into the housing before buying.
    Each LED bulb equips with 8 pieces High Power 1210 SMD CREE LED Chips, with built-in Load resistors, so they will work properly for European vehicle's parking city lights (position lights), sidemarker lights such as Mercedes, BMW, Audi, etc.


    We have conducted a series of long tests base on a 2004 Mercedes E500, a 2006 Mercedes SLK350, and a 2008 Mercedes CLS500. The LED bulbs will light up perfectly and stay on error-free without flickering.

    W5W canbus led light
    Our products are up to European ROHS standards.We will ensure that the products we sell will be seldom heated, high brightness, normally use ultra-long period of time


    http://www.dgruidi.com/en/can bus led-184.html

    www.dgruidi.com
    #17
  19. PetrolDave
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    PetrolDave Well-Known Member

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    [Jun 27, 2010]
    ^^^^^^^^^^^^^^^^^^^^^^

    Looks like a blatant commercial post to me...
    #18
  20. doug.p
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    doug.p Getting There VCDS Map User

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    [Jun 28, 2010]
    They also dont work !!! you still get the warning - trust me i tried all sorts of combs - the only way tat worked was to use resistors
    #19

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