Troubleshooting Trailer Running Light Circuit Not Working on Curt Trailer Wiring

Question:

New utility trailer. 2016 Taurus SEL. Curt 56093 lighting. No trailer running lights. Car taillamps ok. Using 12 v donor battery verified that trailer running lights do work. Brake and signals fine. Using a 4way plug in tester bright green coming from running lights even when turned off. Good ground all around.

asked by: Greg J

Helpful Expert Reply:

It's possible the converter box has an internal short and that's why the running light circuit isn't working. What you can do first though is try unplugging and replugging in the connections of the harness as sometimes a contact just needs to make better connection. Next thing you can check is use a circuit tester like part # PTW2993 to test for running light circuit voltage on the input side of the box and then again on output when running lights are on. If voltage is going into the box but not making it out then its the box's fault and would need to be replaced.

expert reply by: Jameson C