Boat Trailer Turn Signals Both Blink when Either Turn Signal is Used

Question:

I have a 4 pole off the truck 5pole off the trailorwhich I have a 4 wire adaptor I have matched the 2 green 2yellow 2white then connected that white wire to trailor for ground green/brown and yellow/brown to brown both trailor lights flash when using either left or right turn signal , o brake lights when applying the brake

asked by: Scott J

Expert Reply:

The problem with wire color is there isn't really a standard so the functions could be anything. The best thing to do would be to test the wires on the trailer side since the 4-Way flat functions on the vehicle side should be typical of a 4-Way.

To test the wires on the trailer there are a couple of different methods. First, you could trace each wire back to see where it ends and then make adjustments as needed at the connector. The other way is to use a separate 12 volt battery and use it to apply power to each wire in turn to see what lights up and adjust accordingly.

If everything is wired properly then it is likely there is a ground issue or possibly a short. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light but could show up in other circumstances.

For a short, make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H