Troubleshooting Curt Trailer Wiring Harness C55513 That Left Turn Signal Stopped Working

Updated 09/01/2026 | Published 08/18/2026

Question:

I purchased and installed this in 2023. For the past year, the left turn signal has not worked. The left brake does work, which is puzzling. Is the control module broken? Do I need a whole new unit? Or could it be something else?

asked by: Alex C

Expert Reply:

Hey Alex, welcome back! Based on what you described yes it does sound like your Curt trailer wiring harness part # C55513 is damaged and needs to be replaced. You might get lucky and just need to reseat the connector on the left side but I doubt it's that. When a converter box fails it's common for a single circuit to stop working and the solution is to replace the entire thing. Is the wiring on your trailer solid? Usually a short on trailer wiring is what takes them out.

expert reply by: Jameson C

8/26/2026

Sounds like Jameson gave good advice. If all connections are good, then it’s probably the converter box. I haven’t had any issues with mine.

Jameson C.

8/26/2026

@Rp glad yours is working well!

Terry

8/26/2026

Sounds like your controller is burnt! No issues out of mind so far.

Jameson C.

8/26/2026

@Terry I would agree!

Len Y.

9/1/2026

Alex, I feel Jameson is correct to reseat the connector on the left side and maybe look at the left side that attached from the vehicle to see if there's a broken wire. Checking the trailer itself with another vehicle will help see if the trailer wiring is your problem. If you have done that then the module is not working and you need to replace the Curt wiring harness. Good luck, Len