Troubleshooting Running Lights On Enclosed Trailer That Only Work Sometimes

Updated 01/27/2026 | Published 08/24/2024

Question:

So I have an enclosed horse trailer and sometimes the running lights will work and other times they won’t. Brake lights and turn signals always work and this is the case with all three of the vehicles I’ve plugged into. It could be as simple as hitting a bump in the road and they’ll turn on or off. where should I start looking?

asked by: Isaiah S

Expert Reply:

Hello Isaiah. There are a few things that could be causing this. The first thing I would check are the pins on your trailer connector, and on the vehicles connector. Rust or corrosion on these pins can cause certain lights to work while others don't. Clean up or replace the connector on both sides as needed. Another thing to do is check your ground. A bad ground can cause all kinds of lighting issues, and this is quite frequently the cause of similar issues. If all of that checks out, I suspect a short on the trailers running light wire. Trace the wire from the running lights and be on the lookout for any damaged, frayed, or kinked wire and replace as needed.

expert reply by: Jesse M

Jesse M.

1/27/2026

Hey Isaiah, did cleaning the connectors or checking the ground fix the running light issue on your horse trailer? Your update could make it easier for others dealing with the same kind of wiring problem.