Troubleshooting Malfunctioning Marker Lights on Trailer

Updated 05/11/2015 | Published 05/09/2015

Products Featured in This Question

Peterson Trailer Tail Light Kit - Waterproof - Stop, Turn, Tail - Incandescent - Oval - Red Lens

(1150)

$12.38

Hook Probe Circuit Tester

(65)

$12.94

Question:

Why isnt my marker light working

asked by: James W

Expert Reply:

First, check to see if any of the other marker lights are working. If not, check that the running lights are working at the rear of the trailer, as they're all on the same circuit.

If none of the running/marker lights are working, unplug the trailer and check the running light pin on the vehicle's trailer connector while the headlights are switched on, using a circuit tester like part # PTW2993. If you get power on the running light pin, the problem is in the trailer wiring.

If it's just the single marker that isn't working, first check the wiring connections. Make sure the power and ground connections are tight. Some lamps get their ground from a wire connected to the trailer frame, others from the mounting stud being in contact with the trailer frame. Use the circuit tester on the power wire to ensure power's reaching the lamp. Check the bulb to see if its burned out or if the bulb socket is corroded.

If none of the running lamps are working, check the connector on the trailer for damage or excessive corrosion. Trace the running lamp circuit (usually a brown wire) from the connector to the lamps. Look for pinched wires or loose connections.

I'll link you to our trailer wiring troubleshooting FAQ article.

expert reply by: Mike L