Lights on Trailer Go Out When Turning Left  

Question:

Expert Reply:

This sounds like a ground problem or a loose or broken wire that acts up when you are turning left. First, disconnect the trailer and use a circuit tester to test the pins on the vehicle side connector to make sure everything is working properly. If you need a circuit tester you can use # PTW2993.

Next examine the pins on the vehicle and trailer side connectors and look for any dirt and corrosion that could be causing a bad connection and clean it out. Find the main trailer connector ground and make sure it is attached to a clean and corrosion free bare metal surface.

Next do the same ground check for the trailer lights. If you do not see ground wires for the lights, then they probably ground through the mounting studs. If you have a tilt trailer or folding tongue you may need to extend the ground from the lights to the main trailer ground.

Next trace the wires back to the lights and look for any breaks in the wiring. If you do not see any obvious problems, connect the trailer and test the wires as you work your way back to see if there is a break you cannot see. Since the problem occurs when you turn left you may need to also physically move the wires around (the jiggle-the-handle method) to reveal the troublesome area.

If the lights are going out just when the left turn signal is on, then it is most likely a bad ground on the left side taillight or a short along the turn signal/brake circuit or taillight circuit on that side. Also make sure there is enough slack in the wiring between the trailer connector and the vehicle connector to account for making turns.

expert reply by: Michael H

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