Tying Into The Dome Light Power?

[rblock50]

Like many folks in these forums, I hate the lack of interior lighting and I was hoping to see what can be done about it. I know there are the options by IAG and Mabett, but I was hoping that I could somehow tap into the power in the dome light and run some additional lights from there. I know from reading other posts and we can't simply tap into the power and expect the lights to come on/off, its has something to do with the new tech (CAN Bus I think). So I was hoping that I could tap into the power between the physical switch itself (inside the dome light) and the LED lights. If I could do that, then in theory the switch would control the dome LEDs and anything I pigtailed off of it. I was able to do that with my Mabett light, but I think I fried it, so I thought I'd try the OEM one.

I mustered up the courage to dremel out the dome light so that I could get into the electronics. I guess I was hoping for some wires to connect with, but of course it's all microchips and whatnot. I found that some of the parts were indeed hot, but were just passing in the power from the car, and the power didn't go off when the switch was off.

Here is the light without its casing:

Is anyone more familiar with electronics and could help decipher what's doing what here? I had tried my tester in all sorts of places, and just couldn't find the switched power to tap into.

If we can figure this out, I'll make mine the guinea pig and run some more LEDs off of it and report back. I'd rather do this than the IAG and Mabett options.

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[Figmo]

Before we begin: I’m not an expert on any of this but…

As I understand it - modern vehicles use the CANBUS for this. It’s not an old-school switch that either has +12V or 0V. The wire harness is connected to everything. All the time. A digital signal is sent down the harness with a command for a certain device - the device recognizes it’s command and acts accordingly. Think computer network.

Because of this - you won’t be able to just splice into some wires to add additional lighting. You’d require circuitry to decode the command for dome light and then trigger a relay to turn on your new lights (which, I assume, is what Mabett is doing)

However - have you looked at the back side of the LED’s on that circuit board? Perhaps you could de-solder those LED’s and tap into the power that is being fed to them. You might be able to power a couple more LED’s this way. But I doubt the power relay on that circuit board provides enough amperage to go too crazy.

 

[Ksjrb03]

What you’re trying to do can’t be done. With spicing wires anyways. The lighting uses Lin-Bus network, basically a poor man’s can-bus but works on the same principle. Each light is a node on the network.

The light fixtures are 3 wire, one is the battery saver 12+ circuit. As you found, that one stays hot for 60 minutes after the lights turn off. This is what turns the lights off for you if you forget and leave them on. The other Wire is a signal wire, you will only find minuscule voltage on this one. It’s a digital signal telling which nodes to turn on or off, and at what % 0-100. This is how the lights dim. The 12+ is powering the lights, but the signal is telling it when and how bright.

None of this is usable to splice in some new LEDs like you’re wanting.

 

[Theherofails]

Everyone else is correct, I had a small nick in my brake light harness and the module was able to detect a small drop in current to the brake lights.. I actually got an error code for that.

This vehicle is watching everything at all times. You won’t be able to splice in to anything but aux power without the vehicle throwing codes. You won’t get a check engine light, but it’s there.

 

[rblock50]

I understand that the lights receive the signal to turn on through that CANBUS. But I was hoping there had to be a way to tie into the power between the "controller" and the lights. Something like this, but I guess it's not possible since the LEDs are built into the circuit board vs having some wires that I could tap into or find the switched side of the controller. Darn.

 

[da_jokker]

Well Maybett did it... So although the common person may not be able to, maybe someone can design a relay that is triggered off dome light plug. Basically a little box that you run 12 volts to that gets turned on whenever the car sends the voodoo signal that would have normally turned on the dome light.

 

[Ltjb8]

Watch the video post #1:
https://www.bronco6g.com/forum/threads/transistor-irfp-9140-mosfet-for-interior-lights.66956/

 

[Chicoricopico]

With kids and car seats in the back, one of my biggest complaints about the Bronco was the lack of light in the cabin.

I just completed install of the IAG LED Interior Dome Light, phenomenal product and super detailed installation instructions. This product delivers big time . In most cases I’d rather pay someone to do these things but am handy enough to handle a DIY project when it calls for it.

 

[GroovyGeek]

I think that the Mabett light (or equivalent) does good enough job for the cabin but not the trunk area. As discussed above the dome light seems impractical to splice into but it appears that the trunk light is hackable

CORRECTION - the video is inaccurate. The light strip does NOT turn on/off with the trunk and doors.

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