Everything Works but the Right Turn Signal on the Trailer

Updated 08/19/2026 | Published 04/20/2025

Question:

Everything working correctly but the right trailer light isn’t blinking. Thoughts?

asked by: Scott K

Expert Reply:

Hi Scott, I believe you are referring to the right trailer turn signal so I am going to help you troubleshoot based off of that assumption. Please let me know if I am misunderstanding.

A few months ago a co-worker was having the same intermittent issue with his turn signal and turns out the bulb inside of his light was loose. What we did was, pull the right trailer light housing, remove the bulb, and inspect it. Try swapping it with the left one to see if the issue follows the bulb.

If that isn't the issue, you are going to need to do some more testing with a circuit tester. Use a circuit tester or multimeter on the tow vehicle’s trailer plug. Turn on the right blinker and check if you're getting power to the corresponding pin. The right turn pin is normally in the 1 o'clock position on a vehicle's 7-way. If you are getting power there than it's probably an issue on the trailer side. If you don't have power there, you may be missing a fuse.

Inspect the trailer side wiring really well. Check for any frays or damaged wire especially on the right turn signal wire. If you are getting intermittent blinking on the turn signal, you could have a bad trailer ground. That is a very common issue with trailer wiring. If you go through these steps and you are still having trouble please let me know and I can keep troubleshooting with you.

expert reply by: Heather A

Heather A.

9/26/2025

Hey Scott, did you have a chance to try swapping the bulbs or testing the trailer plug with a circuit tester? I'm asking because your experience could help others facing similar issues with their trailer lights.

Joe

8/19/2026

I HAVE HAD THE SAME PROBLEM. EVERYTHING IS FINE AT THE RECEPTACLE OF THE 2017 F250 UNTIL WE CONNECT A TRAILER, THEN WE LOOSE THE RIGHT TURN SIGNAL ON THE TRAILER. THIS HAS HAPPENED WITH ANY TRAILER WITH A 7 PRONG CONNECTOR. WE ALSO PLUGGED A 7 PRONG TRAILER PLUG TESTER INTO THE TRUCK AND IT ACTS THE SAME, NO RIGHT TURN. SO I AM FIGURING THAT IT IS NOT A TRIALER ISSUE. WE HAVE NOT CHECKED A 4 PRONG TRAILER PLUG YET, BUT I AM PRETTY SURE IT IS SOMETHING IN THE TRUCK.

Heather A.

8/19/2026

@Joe Hi Joe, based on everything you’ve tested, I agree that this sounds like an issue on the truck side rather than with the trailers. The fact that the right turn signal works at the 7 way until a trailer is connected, and you get the same result with multiple trailers and a 7 way tester, is a pretty good clue that the circuit is failing once a load is placed on it. On your 2017 F 250, I’d start by checking the trailer tow fuses and relays associated with the right turn and stop circuit. I’d also inspect the 7 way connector and the wiring behind it for corrosion, loose connections, or damaged wiring. A circuit can sometimes show voltage with nothing connected but fail as soon as you put an actual load on it, so testing that right turn circuit while the trailer is connected would be especially helpful here. Have you noticed any corrosion or moisture inside the truck’s 7 way connector, Joe?