How to Test Trailer Wiring Converter Box

Updated 01/19/2016 | Published 01/18/2016

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

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Hook Probe Circuit Tester

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Question:

Have a 1994 Toyota Pickup. Trailer is 2003 Fleetwood pop-up. Hauled it home with 2003 Tundra, all lights worked fine. Hooked it up to my truck, all running lights work but no t/s or brake lights. My test light works at the rear of trailer with t/s and brake. Put bulb in and lights blink. Turn off blinker and retry, will not work. Re did my ground still inop. Ran a ground wire fro neg side of battery to harness, still, no lights. Is it possible the converter is bad?

asked by: Mike

Expert Reply:

There is a possibility that your trailer light converter has gone bad. Testing it is pretty easy.

What you will want to do is test the wires going into the box of the converter box for voltage with a circuit tester like the # PTW2993 to see if there is voltage going into the box when the taillight functions of your vehicle are applied, and then test the output side of the box to see if the current is making it through the converter. If not then the problem is that the converter box has shorted itself out and would need to be replaced.

Before you replace it you will want to inspect the wiring of your trailer to see if you can find anything that would cause the box to short out like corrosion or cut/exposed wiring. These boxes don't usually go out unless there is a short on the trailer that takes it out.

If there isn't input voltage for the converter then the problem is the wiring of the wiring kit. You will need to check to make sure it's making a solid connection to the correct circuits.

expert reply by: Jameson C