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LED Trailer Lights Troubleshooting Lowes Trailer And 2008 Ford F-150


Good morning. I have a question about my Lowes trailer that I just replaced the incandescence lights with LED. They come on. They flash when the hazards are on. They stop blinking when I press on the brake. Same goes with the turn signals. They work till I press on the brake. I checked the grounding wires on the trailer. I made sure I connected all the wires properly. I took it to a trailer dealership and they tested both the trailer and truck plugs. They work. I have a 2008 F-150 Ford. Any ideas? Thank you and have a Merry Christmas.


Expert Reply:

Since you have already checked some of the first troubleshooting boxes, the next place to look is if the harness has been overloaded due to excessive draw from lights or there's a short in the trailer wiring.

Inspect the wiring for any damaged areas where copper is visible or any spots where the jacketing on the wire is broken and replace as necessary. If you've already taken this step, I would next check your harness instructions for maximum amperage rating to make sure you're not overloading it. If the trailer lights are overloading the harness, it is possible that the unit can be reset if the overload is not extensive. Remove the fuse from the power line and leave it out for 30 minutes before reinstalling it. Then, use a circuit tester to check for function at the 4-Way plug. Do not plug in the trailer before testing the vehicle's 4-Way plug.

If all functions are present after resetting the unit, this indicates that the trailer may have a short that is causing an overdraw on the system, or that the trailer lights draw more amperage than the harness is rated to handle. Try removing bulbs from additional clearance lights and connecting the trailer to the vehicle. If the harness continues to work correctly with the bulbs removed, this points to an overdraw from the amount of lights on the trailer. Remove some clearance lights if possible or replace lights with the LED versions which draw much less power.

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