Troubleshooting Vehicle Fuses Blowing When Trailer Coupler Connects to Hitch Ball
Updated 11/18/2020 | Published 11/16/2020 >
Products Featured in This Question
Question:
My running lights on trailer works fine but second I connect to the ball hitch it blows the running and tail light fuse on truck. Any idea of what’s causing this?
asked by: Jackson
Expert Reply:
It sounds like there is a short somewhere in the wiring. First, make sure that both the vehicle side and trailer side connectors are free of dirt and corrosion. If the connector is corroded or dirty, it can cause excess power draw and blow a fuse. Simply clean out as needed.
To start testing on the vehicle, you will want the change all of the blown fuses and then using a circuit tester like # PTW2993, test the vehicle side connector. You'll need some help so someone in the vehicle can run through the functions while you test each pin on the connector. If you detect any power to a circuit when there should not be any, then you know there is a short somewhere on the vehicle side. Simply trace the wiring back from the plug and look for any exposed areas that might be touching bare metal. If the vehicle harness is damaged, you can also replace it using the Curt # C55379, which is a plug and play harness that's easy to install.
If everything checks out fine on the vehicle side, then you will want to check along the wiring for the trailer, again looking for any damaged or exposed wiring that might be touching a metal surface. You can also test the trailer wiring for function by connecting each wire to a 12V battery. Lastly, make sure that the main trailer connector ground and all the light grounds are securely attached to clean bare metal surfaces.
If you are unable to find the issue, please let me know and I will be happy to look into this further.
Product Page this Question was Asked From
Continue Researching
- Q&A: Trailer Running Lights Do Not Work but Brake Lights and Turn Signals Do Work
- Article: Trailer Wiring Diagrams
- Q&A: How to Test Brake Controller without Trailer Connected
- Q&A: Recommended Bike Rack and Dual Hitch Adapter for Carrying E-Bikes While Flat Towing
- Q&A: Recommended Flat Tow Setup for a 2026 Ford Maverick
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Q&A: Trailer Turn Signals Both Blink when Just Left Turn Signal is Activated
- Article: Brake Controller Installation: Starting from Scratch
- Article: Brake Controller Installation for 2007 (New Body Style) - 2013 GMC Sierra and Chevy Silverado
- Article: Installing an Electric Brake Controller on 2007-2013 GM Full-Size Truck or 2007-Present GM SUV
- Q&A: Troubleshooting Right Side Trailer Lights Not Working, Left Side Working Correctly
- Article: Troubleshooting 4 and 5-Way Wiring Installations
- Q&A: How to Activate 12V Trailer Power Circuit on 2017 Ford F-350 Super Duty
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)

