DIY ijdmtoy 4th brake light issue

[mcnvgget]

i have a 2018 toyota 86 GT and i got a 4th brake/running light for the oem reverse light but can’t seem to make it work, black is ground but when it comes to the red and blue wire which i’ve mixed around red with red and blue with green and switched, the bright brake light is running and when brakes are applied it turns off or dims but it turns all of my other brake lights on too, or there isn’t a running light but the brake light works so i went with just no running light but brake light works so i clamped the wires together and tried it but nothing worked like what happened? the wire cut through the harness but still. is my light just defective or can anyone give some tips for me?


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[Mr_Eyo]

IIRC, blue is the brake and you have to tap it to the car's brake light harness wire, not the running light wire; that car-side brake light wire only has 12v when you press the brake pedal. Red is the flasher when you tie it to the brake light. Green is the reverse and should plug into the car's reverse harness.

[BaBaFlyingSheep]

Originally Posted by mcnvgget

i have a 2018 toyota 86 GT and i got a 4th brake/running light for the oem reverse light but can’t seem to make it work, black is ground but when it comes to the red and blue wire which i’ve mixed around red with red and blue with green and switched, the bright brake light is running and when brakes are applied it turns off or dims but it turns all of my other brake lights on too, or there isn’t a running light but the brake light works so i went with just no running light but brake light works so i clamped the wires together and tried it but nothing worked like what happened? the wire cut through the harness but still. is my light just defective or can anyone give some tips for me?


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I finally installed my iJDM 4th brake light, and it will not work out of the box (at least for the newer version that uses a rubber grommet).

What you need to do is add a diode that can handle over 12V and 1A. I used a 1N4004 diode, and tried a few other diodes that tended to work as well. Only one I couldn't get working was a 1N5817, which I think was supposed to work, maybe my diode was defective?

Also, keep note that diodes are directional. So, direct it where the power sources goes into the brake light (for the red wire) and connect it to the green wire (in the BRZ), blue wire on the light connects to the red wire in the harness, and black is with black. Again, iJDM doesn't really know what they're doing, so they switched the wire colors and got rid of a necessary diode for the brake light to work.