Plugged Trailer In, there Was a Spark, Now Trailer Lights Will Not Work

Updated 02/10/2015 | Published 02/09/2015

Products Featured in This Question

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

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$34.94

Hook Probe Circuit Tester

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$13.33

Question:

I hooked up a bumper pull trailer and got a spark from the plug now my lights do not work and there is no blown fuses in the fuse box in the cab of my truck what could be the problem

asked by: William

Expert Reply:

It sounds like there is a short somewhere in the trailer wiring and when it was plugged into the new trailer connector it blew the converter box, which protects the vehicle wiring from this exact situation. You can test to see if this is the problem. First, you will need a circuit tester such as # PTW2993. You will test the wires going into the converter box from the vehicle while someone sits in the vehicle and operates the lights one at a time.

If the signals going into the box work, then test the wiring on the output side of the converter and if there is no power there then the converter is bad and will need to be replaced. But before plugging in the trailer again you will need to find and fix the short.

Make sure the trailer connector is clean and free of corrosion. The main ground and the grounds for all of the lights need to be attached to clean and corrosion free bare metal surfaces. Check the wiring for any pinched or frayed wires and fix as needed.

If the wiring on the vehicle side is correct going into and coming out of the converter box and there are no fuses blown it could be a bad relay, if your vehicle uses relays. Use the vehicle owner's manual to find the location of all fuses and relays.

expert reply by: Michael H