Troubleshooting No Running Lights on Trailer  

Question:

Expert Reply:

There are a number of possible reasons as to why the running lights are not working on your trailer.

I recommend first using a circuit tester like # PTW2993 to test the vehicle side connector while you have a buddy sit in the cab and run through the lighting functions. If you find that you do have power at the running lights circuit with the running lights on, then you at least know the issue is somewhere on the trailer side. If you do not receive power at this pin, then the problem is somewhere on the truck side.

While you are at the connector, I recommend inspecting it for any built-up corrosion or debris, cleaning as needed. You can do the same thing on the trailer side connector.

If you did not get power at the running lights circuit on the vehicle's connector, you will want to check for any damaged or missing fuses. You can use your owner's manual for specific fuse locations related to trailer lights. Otherwise, you will just need to trace along the wiring to check for any exposed or damaged areas, replacing if needed.

Then, on the trailer side, check to make sure your ground connections are made to clean, bare metal surfaces free of any dirt or corrosion. Also check the ground connections on the light assemblies themselves, whether they use a dedicated ground wire or simply ground through their mounting hardware. If the grounds are good, inspect the running light wire along the trailer for any damaged sections.

If you are still unable to resolve the issue, please let me know and I will be happy to look into this further. I have also attached a wiring troubleshooting article that you might find helpful.

expert reply by: Chris R

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