Troubleshooting Brake Lights and Turn Signals Not Working on Trailer

Question:

Have running lights but no brake or turning signals. What fuses control this?

asked by: Char

Expert Reply:

Without knowing what your tow vehicle is, it would be impossible for me to tell you what fuses control those circuits. If your vehicle has dedicated towing circuits, which would mostly be found on a vehicle with a factory installed trailer towing package, you can check your vehicle's owners manual to find out the fuse box diagram for the dedicated towing fuses. With that said, there are a few things you can check out in the mean time that may help you get your brake lights and turn signals up and running again.

I would start by checking the ground wire and make sure that the ground wire on the trailer is firmly connected to a paint and corrosion free spot on the trailer. If that doesn't correct the issue I would then recommend using a circuit tester like the # PTW2993 to check your vehicle's 4 way or 7 way trailer connector to see if power is getting supplied to those pins. If they aren't getting power, the most likely source is a fuse and you can change them out in the vehicle. If you are getting power on the vehicle's trailer connector your issue is going to either be on the trailer connector or the trailer wiring itself.

If those steps don't address your problem, please let me know what your tow vehicle is and I can help you continue to troubleshoot.

expert reply by: Erik B