Troubleshooting No Trailer Turn or Brake Lights with 2015 Ford F-250  

Question:

Expert Reply:

There are a number of possible reasons as to why the trailer turn and brake signals aren't working with your 2015 Ford F-250, and depending on how you're currently testing the lights the issue could either be on the truck or trailer side.

To start I recommend using a circuit tester like # PTW2979 to test the 7-Way on your F-250. Test the brake/turn signal pins on the connector while you have a buddy flip on those functions in the cab. If you get power on the tester you know the problem is somewhere on the trailer. If you don't get power then you can focus on the truck.

If you didn't get power at the connector the first thing I recommend checking is the fuse box under the hood. Check the owner's manual for your F-250 and look for the locations of any relays or fuses related to towing and check to make sure they don't need to be replaced. If these look good then it's really just going to be a matter of inspecting any factory trailer wiring you can access starting at the back of the 7-Way, looking for any frayed, damaged, or pinched areas that need to be addressed.

If you did get power when testing the connector then you can turn your attention to the trailer. First check its 7-Way connector and inspect it for any debris/corrosion that might be built up inside or around the pins and clean out as needed. Make sure all the ground connections on the trailer, both with the main wiring harness and with the light assemblies themselves, are securely attached to a clean bare metal surface.

If you aren't able to locate or resolve the issue please let me know and we can continue to troubleshoot.

expert reply by: Chris R

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