Trailer Lights Not Working After Installing Curt Wiring Harness on a 2011 Ford Flex  

Question:

Expert Reply:

The first thing to check is if the Curt trailer wiring harness # C56343 for your 2011 Ford Flex is sending power through its converter box to the 4-Way like it is supposed to. Use a circuit tester such as # PTW2993 or a meter if you have one to test all of the input wires going into the converter box from the vehicle.

Have someone sit in the vehicle and go through the various light functions while you test the input wires. If something is not showing power when it should on the input side, then the issue is on the vehicle. But if everything does check out fine on the input side move on to checking the output side (4-Way end).

Do the same test on the output side and if there isn't power when there should be then the problem is inside the converter and the wiring harness will need to be replaced. If everything is working as it should then the issue is on the trailer side.

On the trailer side there could be several causes for the lights not to work including a corroded trailer connecter which is the easiest to check. If the trailer has a lot of lights, it is possible, they draw more power than the wiring harness can handle. To test that you would disconnect some lights and if the others start working then you know that was the problem. Switching to LED lights would solve that issue. And last it could be a ground on the trailer so you can check all the grounds, including the individual ones for each light, to ensure they are good.

expert reply by: Michael H

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