Troubleshooting Trailer Running Lights Not Working When Other Functions All Work

Question:

I have a 7 way plug and when plugged into both of my trucks everything but the running lights are operating. What could be causing this issue?

asked by: STephen

Expert Reply:

It is likely that there is a bad ground when only one function isn't working. Check your main ground connection on your trailer as well as the ground connection at your taillights. The taillight ground can often be in the mounting hardware if it doesn't have a separate ground wire. Make sure the connection is bare metal to metal and free of corrosion or debris. You will also want to check your trailer connector to make sure that running light pin is free of corrosion and debris as well. A little sandpaper is a great help. I've attached an article to help further.

If it still doesn't work, you will want to use a circuit tester like # PTW2993 to test the wire and make sure you don't have a short. If you find a short when probing every few feet, replace the wire with # 16-1-1 sold by the foot.

expert reply by: Jason S