I just finished wiring up the lights for my trailer. I used a jumper battery to test everything out before I installed the floor, and everything worked fine except for the right turn signal/taillight. It wasn't as bright as the left one. I'm color blind, so my first idea was that I goofed up the red, brown, green wires. I checked and rechecked every connection. Then I had my Son come check my work. Everything was right, but it still didnt work. Finally he took a hunk of wire and ran it from the stud that holds the tailight to the bracket, and a bare bolt on the frame. TA DA! The 2, 3/8" bolts holding the bracket to the frame that were tightened with an impact wrench didn't provide a good ground. I took off the bracket, reamed out the holes in the frame a little to get off any paint, and put it back together. That did it. I'm new at 12 volt wiring, so maybe this should have been the first thing I checked. I know better now.
Al.