Troubleshooting Trailer Lights that Work Only When Cinder Block is Placed in Back of Trailer

Question:

We just replaced or trailer light wires, weve grounded them and all works well as long as there is weight on the back of the trailer one cinder block does the trick. Without the weight, the lights do not work at all. Any ideas as to why this is happening? We havent tried the lights with a full trailer yet since we are trying to troubleshoot this issue first. Thanks for any ideas.

asked by: Tara C

Expert Reply:

If your lights are working when you add weight to the back of your trailer you likely have a short. I would start off by checking the wiring directly under the location where you place the cinder block. If your grounds are securely connected to a clean, bare-metal surface then there is most likely some wires on the underside of your trailer that have a stronger connection when the block is in your trailer.

Look for any places where the wiring is damaged or pinched and replace it with 16 gauge wire # 16-1-1 and your lighting should work properly.

expert reply by: Jon G