Troubleshooting Trailer Wiring that Works with One Truck But Not Other Yet Wiring Is Good

Question:

We have a 17 ft trailer that we pull with a 1998 Ford F-150. We went to go on vacation, but found that although the running lights work, the signal, brake, and hazard lights don’t. We’ve checked all the ground wires, both plugs and sockets and all the wiring and fuses. We’ve taken it to a trailer repair place as well. Here’s the weird thing. We thought it was our truck, so after going from car place to car place we decided to take it over to my parent’s house to see if it worked with their trailer. We plugged it in and everything worked on their trailer. We brought it back and plugged it into our trailer and the brake and signals don’t work. My dad brings over his F-150 and plugs it into our trailer and everything works. How is this possible?

asked by: Kathy

Expert Reply:

Typically when we see what you described the problem is that the ground for the trailer wiring just isn't sufficient enough to power all of the circuits. What I would recommend is improving the ground circuit wiring on the trailer wiring and vehicle and you should see the circuits all start to work. A thicker gauge wire for the ground circuits will work great or you could also try checking the connections of the circuits on the connectors and vehicle/trailer frame to make sure those are solid and to a clean metal surface.

expert reply by: Jameson C