A dc question if possible, I have a motorbike with a 3 wire led side / brake light. I was planning to add another led light to purely act as a supplementary brake light. When I checked the wires, I have 8v on one wire, (the rear light) 12v on another wire, (the brake light) only when pressed, and a ground wire. I planned to spur off of the 12v wire and ground but when I did i find the supplementary brake led acts like the existing, i.e. it receives 8v with side lights and brightens when brake pressed. How can I make it function purely as a brake light?