Alright guys, Im welding up a flatbed for my '78 and I am going to run the flush mount, 6" oval, LED tail/brake lights out back. I want to run two of them on each side... Here is my issue:
I want to have both of them on each side operate as tail/brake lights, but only one on each side operate as turn signals. That way, on each side, I will have one that is solid bright when braking, and one that is flashing.
Any thoughts on how to make this happen? The turn and brake are on a shared wire originally. I figured I could wire the one that I want to flash, using the original wire, and possibly add another wire that would only supply brake 12v to the second light. But where to get the power? Thanks!

 

Ok the brake light switch, down by the brake pedal, should have 2 wires one will be hot
when the brake pedal is not depressed.
Use a test light to find it.
Then you want to unplug the other. tape it up, it runs to the turn signal switch.
Then you should be able to run a wire from the terminal on the switch that you just pulled the wire off of and taped up.
Run that to your lights in the rear that you want to use as brake lights.
Make sure to run your grounds, should be able to tap in the original ground back there.
When I redid mine I Used 2 and 4 pin connectors like this
http://www.etrailer.com/Wiring/Spectro/9651P.html
http://www.etrailer.com/Wiring/Spectro/9653P.html

Dave

 

How will the turn signals still function?

 

Your going to run the original wiring that was for both the turn/brake to the light that you want as turn signal.
Basically your just adding an extra wire to the original harness to control the brake lights.

Dave

 

Oh! I think I understand. I was thinking that the brake switch was completing the circuit between the two wires, and the turn relay just added an interruption, but really it is completing two separate circuits: Brakes and turns - that ultimately feed the same line. That about right?

 

Yes you have it.
Otherwise if the brake light switch went out neither would work.

Dave

 

You will also need an elecrtonic flasher . The old style wont "flash" with the led's.