Trailer Brake and Turn Lights Not Working

Question:

Right and left turn singles and break lights work on trailer with head lights turned off I put head lights on I get nothing I put a new wire converter on the truck all lights working on the truck with or without trailer plugged in

asked by: David S

Expert Reply:

In most cases when trailer lights don't work with two functions, headlights and brake lights in your case, there is a bad ground. A ground can be strong enough to run one of your functions, but when you are running the headlights as well as applying the brakes or signaling the ground isn't strong enough to run both functions. To resolve the problem you need to find your trailer grounds and sand down the connection points to bare metal. This bad ground could be on the trailer or the vehicle. I would start with checking the grounds on your trailer and if the lights aren't working you need to check the grounds on your vehicle as well.

If you are still having the problem after trying grounds, there could be a short in the wires. You need to follow the plug all the way back to the lights and check for shorted out wires.

expert reply by: Clayton O