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Old 10-23-2012
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LED airbag-bulb swap

I recently did an LED conversion for the whole dashboard, including the "passenger airbag off" bulb. I had a 12v plug-and-play that I soldered in just like the original bulb was. The bulb doesn't turn completely off now, though, as it still seems to be lit by some ghost current. I remember reading a quick response from JP7 about a similar problem and he recommended wiring a resistor (with resistance to match the original bulb) in parallel. I tried this with a 15ohm resistor (12 or 13 ohm original bulb), and the bulb starts off a bit less bright, but it does completely turn off. It also gives me a ton of warning beeps when I start the truck now. I've tried a bunch of combinations (only have access to 15 ohms for now) with more and less resistance and can't get it to both turn off and also not make the beeps. what am I doing wrong?

the PnP LED does have a resistor built into it (470 ohms, I think). I assume that I shouldn't remove that even with 15 ohms in parallel because the LED might take too much and burn up? I'm completely confused about resistors with LEDs now. help.

Last edited by tatsuha; 10-23-2012 at 09:51 PM.
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Old 10-24-2012
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You might try testing the resistor on the led to get the actual value and change it out for a resistor with a slightly higher or lower value, maybe 20-50ohms in both directions to see which helps the most.
You may have to give up a little overall brightness to be able to get the led to turn off completely.
Although ohms law dictates how they should work, sometimes it's best to try stuff to see what works best. About the worst that can happen is you burn out a handful of led's.

I never trust any pre-wired led myself, I take a sample from each batch of led's I get & test the actual voltage unless I have a detailed spec sheet on them... and even then I test them. That way I know the characteristics of each led & how it should react.

One thing to note is that although vehicles are considered 12v, when running the alternator can produce 14.5v or more which can totally mess with your calculations.

That's why some of my single led mods may be a little less bright when the truck is off (only getting 12v+/- battery voltage), but when it's running (full alternator voltage of 13.5v-14.5v), they get full voltage & really come to life.

The warning beeps and/or dash indicators should indicate that the bulb is burned out, or that the led's resistors aren't correct. If you run a resistor across the leads, it will basically see it as a short or open circuit depending on the value of the resistors & thus give the warnings. I think once you figure out the resistor value, you should be good to go.

It's been a while since I started doing that mod... but my info probably wouldn't help as I'm sure the led's I use have different specs than the ones you're using.
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Old 10-25-2012
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I'm fine with losing a little brightness. I mostly wasn't sure if I just wasn't getting the resistance value right, or how to fix that.

Basically, I need the resistor in-line with the LED to be the appropriate resistance to keep the voltage at the proper level so I don't burn out the LED, and then I need to adjust the one in parallel to get the overall resistance to be similar to the original bulb (or whatever value gets rid of the beeping)?
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Old 10-26-2012
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I'd just increase or decrease the resistor that's in series with the led, I never like to run a resistor across a circuit as it can create too much heat or even a direct short.

Wish there was a simple answer for ya, but it's gonna be kinda hit or miss until you find a happy medium
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Old 10-26-2012
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I had the same issues, I couldn't get it to go out without going back to the incandescent style bulb unfortunately.
If you find a fix, I would like to know too.

Quote:
Originally Posted by Capriman86
Update in case anyone else runs in to this.

I did remove the LED since it would never fully go out.

I put in this bulb and it is functioning like it should.


12V/50mA Incandescent Bulb
Model:
272-1154
Catalog #: 272-1154


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Old 10-26-2012
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I converted mine to red a while back, and I used a superflux LED with a 1K ohm resistor. I have no issues with it at all.
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Old 10-26-2012
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It seems a hit or miss, there are plenty of people that used the radio shack orange LED with no issues and that is the one I tried, but it always had a dim glow.

There has to be some current still flowing through on some of our rangers, why I don't know.
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Old 11-14-2012
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After a long delay, I finally got back to this issue.

I tried with the bulb soldered directly to the board on the one side, and on the other, connecting it to alligator clip ---> resistor -----> alligator clips ----> circuitboard. This way I could quickly try out different resistors.

The bulb dimmed more (a few seconds after starting) once I got up to around 700ohms, but didn't go out completely. by 1M ohms, the LED would start out extremely dim and stay the same brightness (it normally dimmed within a few seconds of starting). Even though it still had enough to light up, it was enough resistance that the car would give me the dinging alarm. So it seems there's no way to get this bulb to properly go out unless I wire a resistor in parallel, which I agree isn't my favorite option.

Any ideas? Do I need to try some different kinds of LEDs, like maybe the superfluxes as ME00 suggested?
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Old 12-03-2012
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SOLVED: Using the 12v plug-and-play LED with it's own wiring/resistor still intact, I soldered the LED directly in where the bulb was and found that wiring 20 ohms in parallel with the LED was the right amount. The bulb shuts off completely after the initial few seconds of "testing" and doesn't cause the warning beeps.

Less resistance won't work - down to about 10 ohms, the bulb goes out completely and there are no beeps if you turn the car on but don't start the engine, but once it gets power from the alternator, that amount of resistance isn't adequate to prevent beeping. So for those who want to perform the swap, make sure to test by turning the engine on as well.
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