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DRL/ Side light Load Resistors

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by Darren198712, Jan 9, 2013.

  1. Darren198712
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    Darren198712 Member

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    [Jan 9, 2013]
    Right I have had a search on a few forums and it is unclear what load resistor is used for what.

    I have only found DRL's but it would be helpful if someone posts up Numberplate lights and front side lights too

    DRL
    led drl bulbs with resistors installed (pics)
    Claims to use 25ohm 25watts on DRL's

    LED DRL's finally
    Claims to use 10ohm 25watts on DRL's

    B7 Audi A4, S4 and RS4 LED Daytime Running Lights (DRL) | Nick's Car Blog
    Claims to use 25ohm 10-15watts on DRL but in the picture he uses 15ohms 25Watts

    How to fit LEDs to the RS4 B7 DRLs
    does not specify

    I was wondering if someone can post up what they have used?

    Thanks
    Darren
    #1
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  3. Richardesty
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    Richardesty loves quattro

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    [Jan 9, 2013]
    Personally I've used 10w resistors when replacing sidelight bulbs (one per bulb), 25w resistors for DRLs (21w bulbs - one per bulb) - just one of these for a pair of numberplate lamps - and 50w resistors for H11 fogs (one per bulb). All from eBay 'load resistor' search.
    #2
    Darren198712 likes this.
  4. Darren198712
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    Darren198712 Member

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    [Jan 9, 2013]
    #3
  5. Darren198712
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    Darren198712 Member

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    [Jan 21, 2013]
    bump anyone ?
    #4
  6. PetrolDave
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    PetrolDave Well-Known Member

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    [Jan 22, 2013]
    Start by assuming that the LEDs take so little current you can ignore them when calculating the resistor value. Then apply theses two formulae:

    Power = Voltage * Current

    Resistance = Voltage / Current

    Which means: Resistance = Voltage * Voltage / Power

    So for the resistor you need to make sure that:

    Resistor Wattage = same Wattage as the original bulb

    Resistor Ohms = 12 * 12 / (Bulb rating in Watts)
    #5

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