making box that controls lights trailer

Would a lighter oultlet handle that ccurrent demand? Either way i think you would need two flashers! Since it would be two signals! What do you mean by 4 to 3 converter? You're hooking the brake to a push button switch? Could you clarify a bit more? Or maybe someone else will understand better, hopefully they'll reply!commit your way to jehovah and he will act in your behalf. psalms 37:5

Well red is stop and brown is tail and left and right turn signals are green and yellow, which is four wires and a regular plug has green yellow and brown 3wires some call it a 5 to4, if you count the white wire,ground.   I deliver buses,bread trucks, motorhomes,and have to hook up light to my tow car and there are sometimes i cant hook into the lights very well and there are these boxes people make, like this that you have to manualy do both. box and colum for turn, it really matters when you get pulled over ,

The simplest add-on is to run one power and one ground wire to the trailier. Each "signal" wire controls a relay that connects the power to the appropriate tail/trailer wire. EG: - the stop wire/light connects to #86 of a relay with its #30 to "power" and output #87 to the stop light. - LH flasher wire/light connects to #86 of its relay with its #30 to "power" its output #87 to the LH flasher light.

I've tried to find a commercial box to do this but no luck.  I will also build my own; attached is my diagram using a single flasher and allowing the turn signal to work with the brake light applied.Norm