LED dome lights not working properly...

Discussion in 'Interior' started by bahollis, Oct 14, 2010.

  1. JustinToolbox

    JustinToolbox TYF Newbie

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    It has to do with the bcm , you have to put in a add a circuit an a diode . I'm currently working on doing that in my 04 yuk .
    But I don't want to completely cut out the bcm , so I'm going to try an put a diode from the add a circuit to the orange wire to the lights , then a diode on the orange wire from the bcm an see if it works . Don't want to keep the bcm alive all the time but don't want to completely disconnect it .
     
  2. 95escahoe

    95escahoe Full Access Member

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    When I put LED's in the dome lights on my Esky I had to bend the contacts so the bulbs fit tighter then they were fine


    Sent from my iPhone using Tapatalk
     
  3. armentaaw

    armentaaw TYF Newbie

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    Folks I'm new to this forum. Here is what I did and it totally solved my dim issues. I'm not counting on BCM to control the lights. They have been in over a week and no issues.

    What I did was tap into the orange wire that is one of two wires going to garage door opener. That wire is always hot. The orange wire on the three wire side goes to the map lights, vanity lights and rear reading lights. All of which are switched. See photos. 20200204_090801.jpg 20200204_090801.jpg 20200204_090709.jpg 20200204_090723.jpg
     
  4. DougAMiller

    DougAMiller Full Access Member

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    This certainly will work, but what you have done is to bypass the BCM's ability to turn off the interior lights if they are inadvertently left on, hence the name of the circuit that powers these lights - Inadvertent Power (IP). The IP circuit supplies a low level current that is not enough to run down the battery and will not be enough to light a standard bulb, but since LEDs run on much lower power, they do come on, just at a dim level since it is very low power. The BCM senses current drain on this circuit and switches on full power for about 15 minutes (it will stay on if the engine is running until the light is turned off, then it resets). The LEDs do not draw enough current to reach the threshold for the BCM to switch on full power. This is why turning on the vanity lights (with original bulbs) will cause the reading lights to go to full brightness.

    I solved this by adding a resistor in parallel with the LED that draws extra current to trigger the BCM, and then put a capacitor in series with the resistor which basically shuts off the current through the resistor after the capacitor is fully charged. This does cause the reading lights to slowly fade out when you turn them off. How fast they fade out is determined by the size of the capacitor. If you don't put a capacitor in series with the resistor, you must use a large power resistor, like 10W or so. Anything smaller will burn out. Even a 10W is going to get pretty hot. My first configuration without the capacitor resulted in the heat sink on the resistor melting through the plastic housing of the overhead console, and I had to replace the console housing.

    It takes a 22Ω resistor to draw enough current plus the LED current to equal the current draw of a 194 incandescent bulb. I haven't experimented with what the largest resistor value could be used and still trigger the BCM, but the larger value you have, the lower power rating it can have. Lower power rating on the resistor means generating less heat.

    To throw in a little Ohm's Law: Current = Voltage/Resistance and Power = Voltage x Current This is how you determine how many Watts the resistor needs to be rated for.
     
    armentaaw and Joseph Garcia like this.
  5. armentaaw

    armentaaw TYF Newbie

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    Thanks Doug. I was fully aware of the risks bypassing BCM. I carefully considered the other posts that suggest the same set up. I'll probably be so ultra conscious of leaving any lights on that I may be lucky enough not to end up with a dead battery. Just a sidebar note here, I did try using the canbus lights which is my understanding they have resisters in them. They did not work.
     
  6. DougAMiller

    DougAMiller Full Access Member

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    No problem. It's a hassle making LEDs work properly, but I do like the interior lighting better now. The preferred solution would be to modify the BCM software to change the threshold current to a lower value so that the LEDs would trigger Inadvertent Power, but they will never give us that access. It took me months to reverse engineer the IPC software enough to be able to add the Trans Temp gauge and make it functional, I'm not keen on digging into the BCM software.
     

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