Troubleshooting Trailer Running Lights working but no Stop Lights or Turn Signals

Updated 07/14/2017 | Published 07/13/2017

Question:

How can I improve ground on trailer lights, they are basic issue, and what else could the problem be? thanks

asked by: Kevan V

Expert Reply:

When some lights work but others don't, you are correct that an issue with your ground is the likely culprit. Start with the trailer connector on the vehicle and make sure the ground wire coming out of it is connected to clean metal, meaning no dirt, no paint, no rust or corrosion of any kind.

Follow that by moving to the trailer connector and the ensure the ground wire is in an equally solid state, connected to a bare metal surface without dirt, paint or corrosion. With the taillights needing their own ground, you likely have it from the bolts on the light assembly. If so, just be sure the light's housing is attached to the frame of the trailer.

As for what else it might be, you may want to use a circuit tester like # PTW2993 on the vehicle side to test the functions in order to make sure you have everything wired correctly and there are no loose wires. You would need to use an alternate 12V power source to do the same with your trailer. Also check your connectors for corrosion, which can cause issues like yours; for the most part the corrosion can be cleaned off.

expert reply by: Kyle S