trailer left turn signal light not working

I had the same type of problem. left trailer light would work some times. finaly it stopped working. i ahd to change the whole fuse box under the hood. under the panel was a circuit board that was blown. $500.00 to get it fixed

A poor ground on Trailer may cause lights not to work. Getting a good ground contact may require to remove ground wires and re inspecting that paint does not get in the way of making a good contact.

This truck has a separate trailer fuse under the hood,in the fuse center, its probably blown. Your truck signals have a different fuse for them.

Power distibution center part $310.00