Troubleshooting Left Turn Signal Light Not Working on Trailer

Question:

I have a 2017 Ford F250 XL. It has a 7 pin trailer connector on it. When I hook to a trailer the left turn signal will not work on the trailer. All other lights work and all lights on the truck work. Checked fuses and looked for visible signs of damage to wiring as far as I could. Any ideas?

asked by: Welton M

Helpful Expert Reply:

If the left turn signal isn't working on your trailer I first recommend testing the 7-Way on your Ford F-250 with a circuit tester like # PTW2993. Test the left turn/brake pin on the connector (9 o'clock) with that function activated on the vehicle. If you get power there, then you know the issue is somewhere on the trailer. If you don't get power then you know the problem is on your truck.

If you didn't get power at the connector, I recommend first inspecting the connector itself for any debris or corrosion that might be built up inside the pins. Also check the wiring leading back from the connector for any damaged or exposed areas that need to be replaced.

If you did get power when testing the connector then you can turn your attention to the trailer. Inspect the trailer side connector for debris or corrosion. Also make sure the grounds are connected to clean, bare metal surfaces on the trailer frame. Do this for the left side light assembly as well, whether it grounds through a dedicate wire or its mounting hardware. Inspect the left turn signal circuit wiring for any damages areas that need to be replaced.

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

expert reply by: Chris R