3rd brake light works independently of the brake lights. I ran a wire from an add on brake switch and use that for it. I believe I described it all in my original post.OK - that works for brake lights and turn signals together. Now I'm not certain about the third brake light. It doesn't seem to be coming on.
Info... I'm using Demco Stay in Play Duo braking system. I've installed four diodes and wiring for the tail/brake/turn signals. It all seems to be working now except for the third brake light. I wonder if I should use something like what is shown in the link below to bring in yellow and green and use only the red out... or would a third brake light flasher do the same conversion?