All Trailer Taillight Functions Work Except Running Lights
Products Featured in This Question
Question:
No running lights on trailer got power coming out of both trucks got everything but running lights even put a new connector on still nothing follow the line up to the junction box where it meets the wire going to lights and got power there as well it gets lost someplace in trailer Could it be a grounding issue?
asked by: Slade W
Expert Reply:
This could certainly be a grounding issue. When a circuit does not have a sufficient ground, it can cause many different issues. If possible, I recommend checking all of the grounds for your trailer taillights. You will want to make sure the ground has contact with a bare, clean, metal surface of the trailer frame. If there is any rust or corrosion at the light ground, try relocating the light grounds to a suitable location.
Another possibility is that the wire for the running light circuit has been damaged between the junction box and the taillight. If the wire has been pinched, torn, or damaged, then the running light circuit is likely not reaching the light. You can test the wires on the back of the taillights that carry the running light signal with a circuit tester, # PTW2993, to see if they have signal behind the light housing. If there is no signal on the wire here, then it is likely the wire is damaged somewhere along the trailer. Try tracing the wire as much as possible from the junction box to the taillights. If you are able to find the damage, replacing the damaged section of wire will complete your trailer's running light circuit again.
If this does not provide a solution for you, feel free to let me know and I will be happy to provide further troubleshooting steps for you.

Product Page this Question was Asked From
- Trailer Wiring
- Trailer Connectors
- Trailer End Connector
- 0 - 5 Feet Long
- Plug and Lead
- 4 Flat
- Draw-Tite
more information >
Featured Help Information
Miscellaneous Media
Continue Researching
- Q&A: Trailer Running Lights Do Not Work but Brake Lights and Turn Signals Do Work
- Q&A: Troubleshooting No Running Lights on Trailer but Turn Signals and Brake Lights Work
- Shop: Hook Probe Circuit Tester
- Article: Trailer Wiring Diagrams
- Shop: Trailer Wiring
- Shop: Camper Tie-Downs
- Shop: TorkLift Camper Tie-Downs - Custom Frame Mount - Front
- Video: A Closer Look at the Hook Probe Circuit Tester
- Q&A: Running Lights are not Working on a Trailer with a 4-Way Flat Trailer Connector
- Shop: Thinline LED Trailer Tail Light - Stop, Tail, Turn - Submersible - 11 Diodes - Red Lens
- Video: Comprehensive Review: Thinline LED Trailer Tail Light
- Article: Troubleshooting 4 and 5-Way Wiring Installations
- Q&A: Solution for Trailer Running Lights Not Working on 2012 Nissan Frontier with Tow Package
- Shop: 60" Long Safety Chain with 1/4" S-Hook with Latch - 5,000 lbs - Qty 1
- Search Results: 3031~p
- Q&A: Trailer Marker Lights are Not Working But All Other Lights Work
- Q&A: Trailer Running Lights Keep Blowing Fuses when Turned On
- Shop: Tekonsha Custom Wiring Adapter for Trailer Brake Controllers - Dual Plug In
- Shop: Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Video: An In-Depth Look at the Optronics LED Trailer Tail Light-STL72RB
- Shop: Fulton Boat Trailer Jack w/ Wheel - Sidewind - Swivel - 10" Lift - Zinc - 1.2K
- Video: Set up: T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector on a 2012 Nissan Frontier
- Search Results: d3101
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Article: Wiring Trailer Lights with a 4-Way Plug (It's Easier Than You Think)
- Q&A: Working Running Lights, But No Turn Signals or Brake Lights On Trailer
- Search Results: safety cables
- Search Results: power cord
- Search Results: tow bar
- Search Results: tow bar cover