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Testing a Malfunctioning Wire Harness on a 2012 Ford Escape


Hello, I bought a T-One harness Part#118561 for my Escape March of 2018. It worked great up until now. Now when I plug my trailer in the trailer brake lights light up without hitting the brake. The turn singles dont work....its just brake lights on all the time. Any suggestions?


Expert Reply:

This can be caused by one or two things. As this is an electrical component, they can wear out and fail over time. Most of the time this happens, however, the lights simply do not work at all. Though this may still need to be replaced, there are a couple things to check before jumping to this option.

What you will want to check all your ground connections. This should be done on the vehicle and the trailer. These can become loose and corroded over time making all sorts of odd things happen. If this has happened to one or more of the connections, you will need to clean the area as much as possible and reinstall them, making sure they have a solid connection to bare metal. If this does not get everything working properly, you will need to check the ports on the 4 Flat.

Using a tester like the # 40376, you will need to make sure the port with the green wire is pulsing when the right blinker is engaged and the port with the yellow wire pulses when the left blinker is engaged. Both of these should also trip a tester when the brakes are engaged. The brown wire will be the running lights and should have power running through it at all times, but should not be pulsing. If any of these is not testing properly, it will confirm that the # 118551 needs to be replaced.

expert reply by:
Lazer S

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