Troubleshooting Trailer Running Light Circuit Not Functioning on 2019 Ford F-150
Question:
When plugged in the brake lights and turn signals work and the brake control works but the running lights quit working. What is the best process to find the problem?
asked by: Ken P
Expert Reply:
First thing you should do at this point is test the 7-way of the wiring harness with a circuit tester part # PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached.
If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue.
Make sure that the trailer side connector are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.
If the problem is on the vehicle side then I would first recommend you double check how the harness is installed on your vehicle, make sure all of the connections are good and tight. You should check all towing related fuses and relays as well.
Products Referenced in This Question
Product Page this Question was Asked From
Ford Replacement OEM Tow Package Wiring Harness, 7-Way
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- No Converter
- Custom Fit
- 7 Round - Blade
- Tekonsha
more information >
Featured Help Information
Instructions
Miscellaneous Media
Continue Researching
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- Article: Trailer Wiring Diagrams
- Q&A: Replacing A 125255UC Double Lip Grease Seal
- Q&A: Trailer Hitch Receiver and 4-Way Flat Vehicle Wiring Harness For a 2024 Ford Maverick
- Q&A: 2018 Ford F-250 Super Duty In-Bed 7-Way Socket Recommendation for Slide-In Camper
- Q&A: 7-Way Wiring Harness for 2002 Ford F-350 Super Duty with Square Connector
- Article: Brake Controller Installation on a Full-Size Ford Truck or SUV
- Q&A: Location Of Under Dash Brake Controller Port On 2002 Ford F150
- Q&A: Is the Cap for the Valterra Bumper Mounted Carrier Available Separately?
- Q&A: Will A Rota-Flex Pin Box Provide A Better Ride Quality With A Curt CrossWing 5th Wheel Hitch
- Article: Brake Controller Installation on a Ford Full-Size Van
- Article: How to Choose the Right Trailer Hitch Class
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Article: Towing a Trailer? Let's Talk About Brake Controllers