Changing out leds in window control board

Discussion in 'The Projects Forum' started by nwheeler454, Mar 14, 2016.

  1. nwheeler454

    Thread Starter New Member

    Mar 14, 2016
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    0
    Quick question, I am changing out leds in my window controls in a dodge nitro. The ones in there where green and I would like blue. Seems the old ones where running off of 2.1 volts. The new ones need 3.2. I replaced a few of these and the worked for about 20 or 30 mins when they start to flicker then stop working. Sorry this is such a newbie question, I have been a electrician for 19 years but have never messed with electronics. Really would love to get in to it more. Just don't know the best place to start.

    Here is a picture of one of the boards that I already change out the leds in. Like I stated before they do work for a short time, then start to flicker and then nothing. Could I also change out the resistor for something a like bigger to help with this problem?

    Thanks for any help that you can give....
    Led Board.jpg
     
  2. TheButtonThief

    Active Member

    Feb 26, 2011
    219
    38
    The best place to start would be to measure the supply voltage to the board, not necessarily the voltage drop across the LED's. If the voltage drop across the old LED's was 2.1V and the new LED's require 3.2V then each LED's resistor will need replacing, however it's likely to have a smaller resistance if the new LED has a higher voltage drop.

    In order to calculate what resistors you need, you first need the supply voltage. It's likely that you've burned out the current resistors anyway, blue LED's consume more current than green ones and because they're trying to light up with only a 2.1V supply, that'll make them consume even more current. That extra load is pulled through the resistor which may not have the capabilities to handle such an amount. This would explain why they worked only for a little while.
     
  3. nwheeler454

    Thread Starter New Member

    Mar 14, 2016
    3
    0
    Makes sense. The voltage coming from the car is 14.1 when running. So I guess I could start there. Next question is why does it look like there are 2 resistors hooked up in parallel to the led? So I should have to replace both of these also? Just getting into doing this kind of work and figure this would be a easy place to start, seems to be a pretty simple board. Have no problem replacing the resistors also just need to make sure what size to put on and why there are 2 hooked up the way they are.
     
  4. TheButtonThief

    Active Member

    Feb 26, 2011
    219
    38
    It would be safe to assume that these resistors are in parallel with each other and in series with the LED in order to share the power, the manufacturer may have avoided using a single high wattage resistor and opted for 2 lower wattage resistors as they're cheaper and it looks like they have plenty of board space to play around with. Something I regularly do when designing a circuit, resistors start to get expensive above .25W
     
  5. nwheeler454

    Thread Starter New Member

    Mar 14, 2016
    3
    0
    after some reading and looking around it seems like instead of having 2 resistor with 102 ( 1K ohm ) , that I need 2 resistor with 162 ( 1.6K Ohm).So in parallel I would be going from 500 ohm to 800 ohm. Does this sound right to raise the resistance when needing more power but less amp. I wish I would have gotten into this stuff sooner. I just had a window control go into melt down after something went wrong, not a pretty sight or a pretty smell. But determined not to give up.
     
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