Lights Only Work On One Side of Trailer When Connected to 2005 Ford F-150

Updated 10/21/2019 | Published 10/20/2019

Products Featured in This Question

Hopkins Endurance 4-Way Flat Trailer Wiring Harness - 20' Long

(58)

$25.97

Hook Probe Circuit Tester

(72)

$13.47

Question:

When I test my truck 4 pin connector only the left side turn signal and brake light work. The right side turn signal and brake light along with the running lights do not work Is this a harness problem??

asked by: Andy D

Expert Reply:

It sounds like there could be a wiring issue on the truck more so than your Hopkins Endurance # HM48240 4 way connector. Since you've already checked the harness, you likely would have noticed any corrosion or damage to the pins; so I would start by checking to make sure that the wiring harness is connected to everything firmly and that all of the vehicle grounds check out- make sure that the ground is connected to a paint and debris free surface.If the ground checks out, you'll need to make sure the wiring on the right side of the vehicle is not damaged and that there is no exposed wiring touching any metal parts of the trailer's frame. If you're connected to a powered adapter that sometimes comes on a truck with a factory tow package, check to make sure that the connection hasn't been lost there.

If you've gotten this far and still aren't getting power to all of the pins, let me know and I can give you a few other things to check out, but it's unlikely that a new harness is bad- it would usually be cut/exposed wires that are the culprit. I've also attached a helpful article on 4 and 5 way trailer connections that might be helpful to you during your troubleshooting process.

expert reply by: Erik B