The three most possible reasons for your F-150's trailer lights are loose connections, a faulty fuse, or burnt out bulbs. The first two issues can easily be resolved on your F-150, but switching out the bulbs depends on the type of trailer lights you are using. It is important to make sure your trailer lights are in working order at all times in order to help prevent serious accidents.
Park the truck on a level surface and turn off the engine.
Crawl underneath the rear of the truck. To the left of the license plate, under the bumper, is the trailer light connection. Lightly tug on the connector. If it comes out or is loose at all, pull it out and securely plug it back into the outlet of the F-150. Make sure the connector clicks into place.
Test the trailer lights. If they are still not functioning, the issue may be with the trailer light fuse.
Open the hood and locate the F-150's fuse panel.
Lift off the cover of the F-150 with a slotted screwdriver.
Locate the fuse in slot number 33. This is the trailer light fuse.
Pull the fuse out and inspect the metal rod in the middle of the fuse. If the rod is broken, replace the fuse with a new 10A fuse. If the rod is not broken, the issue is most likely with the trailer lights themselves. Consult the trailer light manual on how to replace the trailer light bulbs.
