No Running Lights on Trailer with a 2015 Ford F-350 Tow Vehicle  

Question:

Expert Reply:

It sounds like you may not have power to the running light circuit on your vehicle's connector. Check that all of the functions on the vehicle connector are getting power using a circuit tester part # PTW2992. Have someone sit in the Ford and run the functions while you test each pin of the connector for power. I have attached a photo of the pin configuration of a vehicle side 7-way. If you are not getting power to the tail or running light pin, you probably have a missing relay or fuse in the fuse box. If you are getting power to each pin, the issue is with the trailer wiring.

I checked the owner's manual for the 2015 Ford F350 and the 30 amp running light fuse (or trailer tow park lamps) is located in spot 26 of the fuse box. The relay is located in spot 29. It is a good idea to double check your particular owner's manual to make sure the locations are the same in your Ford as what I found.

If all of the relays and fuses are okay, then there maybe a weak ground connection on the trailer or vehicle side. When there is a weak ground some of the functions will work while other functions will not because the ground is not strong enough to ground the current for all of the functions. Disconnect the ring terminals for the ground connection and make sure they are free of dirt or corrosion. Reground the ground connections to a clean, bare metal surface.

When you check the grounds, check the connectors on the vehicle side and trailer side to make sure they are seated properly. Clean any debris or dirt from the pins to ensure a strong connection. Check the wiring for any damage. Inspect the wiring for areas where the copper is visible or the jacketing is broken. Those sections may need to be replaced.

If you are still having the running light issue after going through these steps, please let me know and I can help you troubleshoot further.

expert reply by: Heather A

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