Boat Trailer Brake Lights Do Not Work when Running Lights are On

Question:

My boat trailer brake lights will go out when I apply the brakes ONLY when the running lights are on. I put new brake lights on my trailer and have had this problem ever since.

asked by: Robert S

Expert Reply:

If your brake lights do not work only when the running lights are on, my best guess is that you have a poor ground causing the issue. So you'll want to make sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion.

This issue could have happened as you were putting new lights on, with the other possibility being that if your brake lights were LED and you switched to incandescent, maybe you have an overload though that seems less likely.

I have added links below to a pair of help articles on trailer wiring, including a troubleshooting guide for you to take a look at. Additionally (with a boat trailer especially), to help prevent any type of corrosion in your connector, and increase its durability and lifespan I highly recommend using Dielectric Grease for Electrical Connectors # 11755.

expert reply by: Kyle S