Troubleshooting Tail Light and Brake Light Issue When Using T-One Vehicle Wiring Harness # 118524  

Question:

Expert Reply:

To pinpoint where the problem is actually occurring, I recommend using a circuit tester to check for function at the 4-Way plug on your 2007 Jeep Liberty, without your trailer connected. We offer part # PTW2993, if needed.

With a helper in the cab of the vehicle and the taillights on, check to see if you get a power reading on the yellow and green wire ports when the turn signal is flipped or the brake pedal is pressed, as these would be the turn and brake signal wires. For example, when you have the right turn signal engaged, you should get a flashing reading on the green wire.

If you do not get a power reading on the brake and turn wires when the tail lights are on, check the white ground wire on the # 118524 wiring harness to make sure that it is firmly attached to a clean piece of metal on the vehicle frame, and that there is no paint, corrosion, or buildup on the ground surface.

If you do get a power reading on these wires and they look to be working as normal at the 4-Way plug, you will know that the issue is on the trailer side. Again, you will want to check the ground wire from the trailer connector to make sure it is cleanly grounded. Most trailer lights will be grounded through their mounting hardware, but you will want to make sure that the grounding point is clean and free of paint, whether they ground through a wire or through the mounting studs. Sometimes even a plastic license plate bracket being mounted behind the light is enough to cause a bad ground connection.

Judging by the way the brake and turn functions work properly when the tail lights are off, I would double check your wiring configuration at the trailer tail lights. If you have the tail and brake/turn signal wires switched at the lights, this would also cause the issue you are describing.

If you have more than two tail lights and two clearance lights on the trailer, you may also be overloading the harness. If so, you could either remove the clearance lights or replace some lights with the LED versions, which draw less power.

I have included links to some additional information on wiring your vehicle for towing, if needed.

expert reply by: Sarah L

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