third brake light?

[turbobooster]

i came across a tail light harness assembly with the 3rd brake light wiring what id like to know is if this can b replaced on a buick that doesnt have the third brake light ? the harness all looks the same except for the connector thats there for the 3rd brake light thanx

 

[Red Regal T]

It just has to light of course, when you hit the brakes and not light with the turn signals. I believe you can get the 12V directly from the brake-light switch that bumps on the brake pedal.