Troubleshooting Trailer Wiring Turn Signal/Stop Circuit Not Functioning

Updated 05/25/2025 | Published 05/18/2025

Question:

I have a question I have a a 2004 jeep liberty trying to haul an LED light trailer with electric brakes, the turn signal and brake lights won’t flash. What do I need to do to remedy this issue?

asked by: Mark M

Expert Reply:

Hey Mark, almost every time a problem like this pops up the solution is to clean the pins of the trailer wiring as some dirt/corrosion is preventing the circuit from being active and cleaning the pins with sandpaper fixes the problem. Try that and let me know if that fixes it or not.

expert reply by: Jameson C

Mark M.

5/21/2025

The contacts ground and everything are clean when I plug the trailer into my brother new Ford F150 they work fine. The garage up the street from me said I need an electronic flasher in the Jeep, the parts store said they don’t make one for a 2004 jeep. The trailer is a brand new sport haven aluminum trailer. My old tailer worked fine with incandescent lighting. Not sure if resistors,is what I need or is there other options?

Jameson C.

5/21/2025

@MarkM You wouldn't need an electronic flasher unit. Whoever said that was confused and thought you put LED lights on your Jeep and not on your trailer. LED trailer lighting does not require the flasher units. I would take a circuit tester like the part # PTW2993 and test the stop/turn circuits for voltage as you travel back from the trailer connector to see what area the circuit stops being active and fix as needed. Most likely there's a break in the wiring.

Mark

5/23/2025

@MarkM I checked the power situation with a tester there is power to my hookup. The one tail/ brake is bright the other one is dim neither work when I depress the brake or blink when I use the turn signal. When I hooked it up to my brothers new ford they worked just fine. I tried to add a resistor to the taillights of the trailer and no change.

Jameson C.

5/25/2025

@Mark It sounds like the trailer wiring harness is bad since it sounds like the trailer works fine with a different vehicle and the circuit tester is showing a brighter light on the one side of the vehicle wiring.