Troubleshooting Trailer Lighting that is Slightly Dimmed with Some Vehicles

Question:

I have a 2013 ford f-150 with trailer towing package and factory brake control. My problem is all electrical functions work perfectly when plugged into my RV. However if I plug into a utility trailer with a 7 prong plug nothing works on the trailer. The taillights are very dim and no turn, stop, or brake lights. A friend plug the same utility trailer into his dodge ram and everything on the trailer worked correctly. Ive read that SAE standard and RV standard are different concerning slight differences as to what wires do what but one of your experts stated that the only difference is the color of the wires. Whats going on ? Any help will be greatly welcomed. BTW, all fuses and relays checked out good on the truck. Thanks.

asked by: HENRY T

Expert Reply:

The difference between the SAE standard and RV standard trailer wiring is only the wiring colors and not functions so most likely what you have is a slightly insufficient ground on the utility trailer wiring which is preventing it from consistently working with all of the vehicles mentioned. First easy to thing to do is take sandpaper to all of the pins on the trailer wiring connector to improve contact there. Next you can try checking the condition of the ground strap that runs from the connector of the trailer to the trailer frame. Make sure it's making a solid connection to the metal frame.

You might have luck running a jumper wire from here to all of the light assemblies to really improve the ground.

expert reply by: Jameson C