Working Running Lights, But No Turn Signals or Brake Lights On Trailer

Question:

Why do I have working trailer lights, but not blinkers or brake lights?? Thanks...

Expert Reply:

You will first want to check the fuses on your tow vehicle. Some vehicles could have fuses for operating the turn signals and brake lights of a towing package. You will want to check if they are installed and working properly.

The next thing is to make sure the wires on the trailer plug is wired properly to the trailer. If you have a 4-Way connector on the trailer the white wire is for ground, the green wire for right turn and brake, yellow wire for left turn and brake, and the brown wire is for running lights. I am including a link to a FAQ page on trailer wiring.

If the wiring is all correct then you will need to check the trailer connector on the vehicle and trailer for a ground connection issue, or a short on the tail light circuit on the trailer. Open them up and make sure there is no white or green corrosion causing an issue inside the connectors. If so clean them out or replace the connectors with new ones.

If the problem is not found in the connectors, you will need to follow the trailer wiring and check all of the grounds for all of the lights and the trailer connector. Make sure each light is grounded to the trailer frame and that the connection to the trailer frame is free of rust, paint and corrosion. Other lights like running lights down the side of the trailer may have a separate ground wire or they may be grounded through the mounting hardware so you will need to check each of these lights.

While you are checking all of the ground connections, it is a good idea to look at all of the wiring and check for pinched cut or frayed wires that could be causing your issue, or could cause an issue in the future.

I am including a link to a troubleshooting video that should help you with locating the problem on your trailer.

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