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Troubleshooting Trailer Wiring on a 2008 Mercury Mariner


Brown wire powered up all the time. When brakes applied, brown wire makes tester dim. Brown wire blinks with one of the blinkers. No power going to any of the two yellow, green wires. Disconnected converter at tail light. Tested cars wiring. All good. Disconnected white ground wire, used sandpaper to clean eyelet and frame. Is this an indication of a faulty converter/modulite?


Expert Reply:

If you tested the wiring on your 2008 Mercury Mariner and it is operating properly but then when you install a wire converter unit the 4-Way flat connector isn't operating properly then yes, I would say that is an indication of a faulty converter/ModuLite wiring unit. In this case I recommend replacing your wiring with the T-One # 118551 as it sounds like you don't have the factory tow package.

I really like the Tekonsha wiring kits because we tend to have the fewest amount of troubleshooting questions when it comes to them. This T-One kit plugs in behind your tail light housing like you mentioned but then it also includes wiring that you route up to your battery so that it is drawing power from your battery instead of the wiring circuits on your Mariner.

Attached is a review video of this wiring kit as well as a helpful article that gives tips on routing wiring to your battery.

expert reply by:
Jon G

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