'79 Gs Third Brake light Install
 

Hey guys i was wondering if you guys knew were the heck i need to splice into for the third brake light to work. It tells me to splice into the green wires on the rear brake light harnes that leads to the brighter side of the bulbs but when i did the light didnt work when i hit the brakes. But when i apply 12v to it it turns on. I got pics of the whole thing but when i finish i will make a step by step post for all you other "anti rear end collision rapping because i didnt notice you breaking" excuse. Thanks....

Per the wiring diragram, the green wire that interconnects the two tailights is the correct wire.

You can't easily tap earlier in the system than that, as the lead you need is part of the black ribbon cable that runs front-to-back.

Alternately, you could pick up the green wire out of the brake light switch itself, and wire all the way to your light.

Where is that switch?

At the top of the brake pedal arm, under the dash.