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Need Electrical Help With BIU Triggered Puddle Light Wiring


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So, the project is to install an accessory exterior puddle light which switches on with the dome light. With the research I’ve done, the way to trigger this to use the brown wire off of the BIU which is an alternating ground.

 

My theory is to tap into that ground using a 12v-87 style relay to use the brown wire as a trigger. When the trigger wire from the relay is grounded, this would power the puddle lights with the way I have it setup.

 

My concern is accidentally frying the BIU...

 

If I use a small 1amp fuse on the relay, Will this diminish the possibility of frying the BIU? I’ve also heard that the brown wire from the BIU also changes into a positive 12v current instead of a ground but I haven’t found much in my research to truly buy into that yet. If that is the case, then it would blow the fuse every time and I wouldn’t be able to continue with this project.

 

Anything helps, thanks!

 

Also if there are other ways to trigger puddle lights with the keys, I’d like to hear suggestions for that as well.

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Yes. I did the map light mod. Great upgrade since my dome light is like 2ft behind my head due to the sunroof. If you do it make sure to follow instructions as they’re posted and use LEDs in place of incandescents to reduce load on the BIU. You may or may not be successful adding puddle light to this mod as I don’t think anyone has info on what the BIU can handle load wise. Maybe if you can figure out the load applied by the single dome bulb and compare it to load applied by the number of LEDs you want to add you may be able to keep yourself from burning up the BIU dome light circuit. BTW Since the BIU fades out the lighting a relay added to the circuit will most likely chatter/buzz as it dims.
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Yes. I did the map light mod. Great upgrade since my dome light is like 2ft behind my head due to the sunroof. If you do it make sure to follow instructions as they’re posted and use LEDs in place of incandescents to reduce load on the BIU. You may or may not be successful adding puddle light to this mod as I don’t think anyone has info on what the BIU can handle load wise. Maybe if you can figure out the load applied by the single dome bulb and compare it to load applied by the number of LEDs you want to add you may be able to keep yourself from burning up the BIU dome light circuit. BTW Since the BIU fades out the lighting a relay added to the circuit will most likely chatter/buzz as it dims.

 

As a you said, it does chatter and buzz as it dims... not entirely sure how to go about this.

 

Maybe I can use the turn signal/hazard instead?

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You could use the device below to set the puddle lights on a timer. If you wire the trigger into the keyless unlock wire and diode isolate it from the unlock door switch side you could have it trigger the lights on for a preset time upon keyless unlock and not when you unlock from the door switch.

 

https://www.amazon.com/Directed-Electronics-528T-Accessory-Pulse/dp/B0009WP09K

 

You may find it cheaper elsewhere this was just for reference

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You could use the device below to set the puddle lights on a timer. If you wire the trigger into the keyless unlock wire and diode isolate it from the unlock door switch side you could have it trigger the lights on for a preset time upon keyless unlock and not when you unlock from the door switch.

 

https://www.amazon.com/Directed-Electronics-528T-Accessory-Pulse/dp/B0009WP09K

 

You may find it cheaper elsewhere this was just for reference

 

I think this might be exactly what I needed. Going to order it and give it a shot.

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Well, that timed pulse relay was exactly what I needed. I still have it triggered by the BIU dome light brown wire. But this relay will hold power to the lights for an adjustable amount of seconds. I have it set to about 15 seconds. Only down side is that it turns on after I close the door too for 15 seconds. Not much of a bother right now

 

I may also use the same trigger for the fog lights...

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  • 2 years later...

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