Troubleshooting Trailer Taillight Kit that Allows Vehicle Lights to Work but Not Trailer

Question:

2017 Ford Transit Wiring Harness available C56327 I just finished hooking up the wiring harness and it does not work. My tail lights still work, and the trailer lights definitely work because I tried my trailer on my other truck. Any suggestions?

asked by: Robert L

Expert Reply:

Since the vehicle taillights still work that means the connectors are fully seated. Most likely the problem is the converter box of the kit then.

What you will want to do is test the wires going into the box of the converter box for voltage with a circuit tester like the # PTW2993 to see if there is voltage going into the box when the taillight functions of your vehicle are applied, and then test the output side of the box to see if the current is making it through the converter. If not then the problem is that the converter box has shorted itself out and would need to be replaced.

Before you replace it you will want to inspect the wiring of your trailer to see if you can find anything that would cause the box to short out like corrosion or cut/exposed wiring. These boxes don't usually go out unless there is a short on the trailer that takes it out.

expert reply by: Jameson C