Why do my trailer lights work with one vehicle but not another?

Trailer Lights Work On One Vehicle But Not Another. Using a circuit tester like part # 40376, you will want to test each pin on the vehicle connector for function to make sure you are receiving a signal. Check for any corrosion in the harness. Any corrosion can cause problems on a wiring circuit.Click to see full answer. Also know, why does only one side of my trailer lights work?If the lights on one side still aren’t working, you may have a break in the wire. To test for a broken wire, check the color of the wire going to the socket and then find that wire on the connector in front.One may also ask, how do you wire up trailer lights? Attach WHITE (ground) wire to trailer frame. Install the YELLOW/BROWN wires along the LEFT side of frame. Install the GREEN/BROWN wires along the RIGHT side of frame. Connect BROWN wires to each tail light (brown). Likewise, people ask, will trailer lights work if not grounded? Expert Reply: In some cases trailer lighting will ground through the hitch ball but that’s typically only if the actual ground circuit is insufficient. It needs to ground through the wiring of the trailer harness.Do trailer lights have fuses?Trailer lights work except for one function: brake, right turn, left turn, or tail. Harness wires are not connected to vehicle correctly/securely. ( Plug-In Only) A set of connectors is not seated together properly or is not making a good connection. ( Plug-In Only) A required fuse or relay is blown or missing.