Right rear turn signal and brake light on 378

Right turn brake light not working on a 1996 378. No power at plug at rear of truck. Anybody know where the next plug is up along the frame is? Front turns work, trailer turn brake lights work so it is in the the harness running the rear of tractor. I figure there is a plug up along the frame maybe under bunk or cab that is the problem.
Any help would nice. Thaks

 

Thanks, but every other right turn on the truck and trailer works. all brake lights work but right rear tractor. Turn switch only year old. I'm going to follow the wiring up along left frame in the morning and see where it goes. There is only 5 wires in it, L/R turn and brake are same 2 wires, 1 for running lights, 1 for back up, and 1 ground.

 

Ok then, I will buy another switch and see what happens.

Thanks