Trailer lights fuse

[dhirocz]

Try the wiggle test. Put a new fuse in it, turn them on, the start wiggling the wires around from behind the trailer connector all the way to the lights. While wiggling, look for anything that might look like it could cause an intermittent short while driving.

Have you checked the circuit with a multimeter?

My tractor did this...I had a broken wire going in to the trailer electrical socket behind the cab.