Trailer Light Problem Troubleshooting Where Blinkers Cause Both Sides to Flash

Question:

Running lights work on trailer, brake lights work on trailer When I turn on right turn signal both trailer lights flash, when I turn on left turn both trailer lights flash, when I turn on hazards nothing on trailer flashes

asked by: Larry R

Expert Reply:

Your trailer lighting issue has to do with a bad ground or connection issue. This could be on the vehicle side, but is much more likely on the trailer side. I recommend checking your trailer main frame ground and making sure it is clean of debris or corrosion and using some sand paper to make sure the connection is bare metal to metal. Then on each tail light, make sure the ground connection is clean in the same way. Often trailer tail lights have the ground through the mounting hardware, so if there isn't a separate ground wire, make sure that you clean the mounting points to ensure a clean ground.

Finally make sure you clean the actual trailer pin connections and vehicle connections with some sand paper. Sometimes slight corrosion causes issues with the signals. Then you can use dielectric grease # 11755 to keep moisture and debris out of the connections for preventing this issue in the future.

If this doesn't solve the issue then it is likely the turn signal wires have shorted to each other which would be rare but not impossible. If that is the case a new wiring harness like # A35W42B is my recommendation.

expert reply by: Jason S