[m510mein]

Ive purchased an aftermarket brakelight and Im stuck on how to wire it. The stock tailight on my sl350 had 3 wires going out to the switches, battery and ignition switch. On This new one it only had a red wire and a black wire so i sent the black to negative battery side and the red i split out to the ignition switch and brake switches. It comes on fine with the ignition switch but no change when the brake switches are engaged. Any ideas?

 

[J-T]

The light you have will work as a tail light or a brake light, but not both. You need a brake/tail light with a dual filament bulb and 3 wires. One wire goes to the ignition for the tail light, one goes to the brake light switch, and one goes to ground. You could also use 2 separate lights.

 

[phil71]

it's possible this fixture is expecting to be grounded at its body, and those two wires are tail/brake respectively. If you look at the bulb, and it's dual element, chances are black is tail +, red is brake +. housing is -