Troubleshooting New 7-Way Trailer Wiring Connector on Trailer with Lighting Issues
Updated 12/22/2025 | Published 10/03/2024
Question:
I have a two horse bumper pull trailer I converted from a 6 pin round to a 7 blade plug. All lights work except when I turn on the running lights all lights come one except one tail light and the brake/turn signals stop working. I’ve checked all light connections, tried a new light for the taillight that goes out works correctly without running lights and checked my harness ground location and cleaned all rust/corrosion from the ground area. Trailer has been tried on several different tow vehicles all having same exact issues, so that should eliminate the tow vehicle. I’m at a loss for determining the cause of my issue. The only wire not connected to anything on my new 7 blade is the purple reverse light in the plug center terminal. I currently do not physically have a reverse light on the trailer. Any advice would be much appreciated. Thanks.
asked by: Brad O
Expert Reply:
Hey Brad, one issue with 6-way wiring that gets a lot of people is that there are two standard 6-way wiring configuration with the only difference being that the 12 volt hot wire and the brake output circuit is swapped. I wouldn't think that is for sure your issue but figured it was worth mentioning.
Aside from that it's actually really easy to create shorts between circuits when installing a new connector so I would make sure that all of the wires at the back of your new connector aren't touching each other. Or there's possibility the pins are wired to wrong circuit.
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Jameson C.
12/22/2025
Hey Brad, did checking for swapped circuits or shorts at the new 7-blade connector help fix the trailer light issue? Knowing what you found could help others sorting through similar wiring problems.