Trailer Turn Signals Blink Opposite Only When the Running Lights are Turned On

Question:

when I have the horse trailer connected during the daytime, the all the turn signals work right. Then when i turn my truck lights on, the trailer blinker lights blink opposite of what the truck is blinking too.

asked by: Tim S

Expert Reply:

It sounds like you have a ground issue. Ground problems show up when there is more load on a system. In this case with the running lights on there is more load on the system when you go to using the turn signals or brakes. You will want to check the main trailer connector ground and the grounds for all of the lights and make sure they are attached to clean and corrosion free bare metal surfaces.

Also make sure that the trailer connectors on the trailer and vehicle side are clean and free of corrosion. Corrosion can cause a short as well.

You will want to make sure that all the trailer wiring is intact with no breaks with exposed copper touching bare metal.

expert reply by: Michael H