Trailer Running Lights Not Working on Trailer Towed by a 2003 Honda Pilot

Question:

Hi, I ordered the trailer harness for my 2003 Honda Pilot from this website and something isnt right. I am unsure that its the actual harness or just my vehicle. I just re-did my boat trailer lights 2 years ago and they work perfectly with 2 of my vehicles, but not my Pilot. I installed this harness and plugged it into the trailer, and the whole right side of the trailer works fine. The left side has a lot of random issues. When I press the brake, the left tail light on my trailer will only light up for a split second and then go out. After that, I cant get the brake light to work on it. The running light works but the blinker does not. After awhile of driving the trailer around, the running light eventually goes out as well. I tested the vehicle wires and it seems like i dont get enough voltage through these wires even though all the lights work great on the vehicle. My car battery is old and has a bunch of corrosion on the posts and connector. Could this be the issue? Otherwise, I have no clue where to track down any ground wires on the vehicles that might be responsible for this. I would literally have to tear apart the interior of the vehicle.

asked by: Cory

Expert Reply:

Some tow package wiring harnesses on vehicles can overcome ground issues better than others. Although the trailer works with other vehicles, since some vehicles are more sensitive about ground issues, a ground problem on your trailer could still be causing the problem you are experiencing.

Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H