HI! All,
Trying to hook up my truck to boat trailer wiring. Bought light setup already wired for trailer with a flat 4 way plug setup. Green-right stop/turn sig, yellow- Left stop/turn sig,
brown for tail lights and white for ground. Located turn signals with light testor.on truck and tail lights. Hooked up ground wire on truck. The stop lights will not work. When brakes applied testor lit up on another wire under my truck. Had nothing to do with the right and left signals .?????????
I am stumped. Can anyone tell me what I am doing wrong please??

 

I have a factory wiring harness on my Ranger and I just tried to test my new trailer wiring. When pushing the brake pedal, the lights went out. When I put the right blinker ON, The two side marker lights flashed along with the right blinker. The blinkers flashed out of sequence with the truck lights, opposite, off when on, on the truck. Flashers did the same thing.

I know this is a old post but it may help someone. Perhaps me. lOL

I tested the same trailer wiring on my Chevy and it worked perfectly.

 

It sounds like it might be a bad ground on the trailer. Check each lamps ground ensuring they're clean and tight.