Troubleshooting Trailer Lights Staying on Constantly

Question:

For some reason my trailer lights stay on after I turn my van off. Also, the break lights and turn signals do not work. All of the trailer lights stay on constantly until I unplug from my van. I have a 2016 Ford Transit 250

asked by: Jonathan T

Expert Reply:

There are a couple of reasons why your trailer lights may be staying on constantly, starting with a corroded connector. What corrosion does is cause a short which can lead to the lights staying on, and when you unplug the connectors they would, of course, turn off. So start by checking there, and if you can't clean the corrosion, you can replace the connectors on either the side of your Transit or trailer.

I'm not sure if you have a 4-way or 7-way but if you have the factory tow package and a 7-way you can replace the connector with the 7- and 4-Pole Trailer Connector Socket # HM40975, or if you have a 4-way, the Hopkins Endurance Easy-Pull Harness with 4-Pole Flat Connector # HM48058.

On the trailer end for a 7-way you can use the 7-Way Molded Trailer Wire Connector # H20043 or for a 4-way the Wesbar 4-Pole Flat Connector # W787264.

The other possibility is just a short caused by damaged wiring on the trailer itself that is causing the power to remain, so you'll want to check your wiring carefully looking for any damaged wires and repair or replace as needed with 10 gauge wire # 10-1-1.

I have added links below to a pair of help articles on trailer wiring, including a troubleshooting guide for you to take a look at. Additionally, to help prevent any type of corrosion in your connector, and increase its durability and lifespan I highly recommend using Dielectric Grease for Electrical Connectors # 11755.