Trailer Running Lights Not Working On a Trailer Towed by a 2011 Ford Fiesta  

Question:

Expert Reply:

It sounds like the running lights are not working on the trailers. Since they are working fine with the other vehicle, this indicates a problem with the other vehicle and/or its wiring harness. You can test the wiring harness to see if it is faulty using a circuit tester like # PTW2993 if needed.

Also, make sure that you are using the correct wiring harness. The hatchback models can use the 56064 but if you have a sedan, you would need a different harness like # 118422 or # C56114.

If the harness you are using has a converter box, test the wires going into the converter first. If they are showing the correct signals, then test the wires coming out of the converter. If the signals are not correct coming out then the converter is bad, and it will need to be replaced.

If the signals are not right going in, this indicates a problem with the vehicle wiring or a bad connection somewhere. Make sure that the white ground wire is attached to a clean and paint free metal surface. You can try moving the ground also. On the 4-Way, make sure the brown wire is showing a signal with the running lights, the green is showing right turn/brake lights, yellow is showing left turn and brake lights. Then make sure the trailer side connectors wires lead to the same corresponding lights on the trailer.

If the trailers have a lot of running lights, it may be too much draw for the wiring. The 118471 harness can only handle a max of 5.6 amps for running lights. If you are using harness # 118422, it can only handle up to 4.2 amps for running lights. Harness # C56114, can handle even less since it is directly connected to the vehicle wiring.

If I did not quite hit the nail on the head as to what the problem is, let me know and I will help you do some more troubleshooting.

expert reply by: Michael H

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