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Malfunctioning Tail Light on Trailer Towed by 2006 Ford Escape


Ive had this wiring harness installed since last summer. 2006 Ford Escape V6 4x4 Its worked perfectly up until this weekend. When I connect the harness to the trailer the driver side tail light on the trailer turns on. It will not blink with the left turn signal or with the 4-ways. It also does not get brighter with the brake lights. It is always on even when the car is turned off. It was working fine about 4 weeks ago. Any idea what this might be?


Expert Reply:

It sounds as if you have a short somewhere in the wiring system. Start by unplugging the trailer, and using a circuit tester like part # 40376 on the trailer connector on the vehicle. You should not show any current coming through the connector unless the turn signals, brake lights or running lights are activated. If there is power passing through even though none of the indicator lights are activated, something in the converter has shorted, allowing the 12v power drawn from the battery to pass through the converter. If this is the case, the converter should be replaced.

More often than not, when a converter shorts out, it is caused by a wiring problem on the trailer. Before replacing the converter, carefully examine the wiring on the trailer. Start at the trailer connector, and work your way rearward to the trailer lights. Check the connector for excessive corrosion or damage. Carefully examine the wires themselves for cracked or worn insulation that would allow the copper conductor to short out to the trailer frame.

I will link you to a video showing how to troubleshoot a converter.

expert reply by:
Mike L

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