Why are Trailer Tail Lights Malfunctioning When Connected to a 2003 Jeep Liberty  

Question:

Expert Reply:

Often when you find that you get lights that are not working at all or performing strangely, the issue is a problem with the ground wire.

Since the same problem occurs on two different trailers, I would suggest first checking the ground wire going into the converter box on the 4-Way wiring harness on your 2003 Jeep Liberty. This wire should be white, with a ring terminal attached.

Make sure that this ground wire is firmly connected to a clean metal point on the vehicle frame, and that there is no corrosion, paint, or buildup between the ring terminal and the frame.

I also recommend using a circuit tester, part # PTW2993 if needed, to test on the taillight and left turn wires, usually colored brown and yellow respectively, as they go into the converter box. I would have a friend in the cab to engage the turn signal for you.

This would help you to better pinpoint exactly where the issue is occurring. For instance, if you find that you have a power reading on the left turn/brake wire, but you find that you are not getting a reading on this same wire at your 4-Way plug, this would let you know that the unit would need replaced, as there is a problem within the converter box itself.

The tail light converters are not user serviceable, so this would just mean that the unit would need to be replaced.

Another possibility is that the connectors installed behind your vehicle tail lights are not seated properly. Check the wiring harness and vehicle side plugs where they meet together, and make sure that you hear a click as they are pushed together. I would also check inside both sets of plugs to make sure neither have any bent pins.

I have included some links to videos and information that should be helpful for you.

expert reply by: Sarah L

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