Troubleshooting Intermittent Trailer Connection 2013 Ford F-150

Updated 05/01/2024 | Published 04/30/2024

Question:

Hi - I am towing a single axle trailer with electric brakes behind a 2013 F150. For two years I have been having a problem where the trailer shows connected, then disconnected, connected, disconnected in random length intervals from 15 seconds to several minutes. The lights still work even when it shows disconnected. The trailer manufacturer replaced the entire wiring harness and brakes. The dealership says there is nothing wrong with the truck. I replaced the fuse, relay, truck wiring harness, both connectors, and the brake controller. Nothing worked. Finally I removed the battery and it stopped disconnecting! It works perfectly! The battery is at 12.3 volts. I haven’t tried load testing it yet, but the tech who replaced the harness said he replaced the battery as well. I’d like to get the battery back in there for safety, but not until I figure out the root cause. Have you ever seen this? Any thoughts on why this is happening? Could it be a bad cell in the battery, or Maybe a bad charger? Thanks, Travis

asked by: Travis

Expert Reply:

Ford F-150's are an odd bunch when it comes to connecting to trailer wiring for some reason. While we haven't seen this exact issue it does not surprise me. It typically has to do with the 12 volt accessory circuit of the trailer wiring though so that would be where I would be inclined to start. If trailer has aluminum frame make sure you have a jumper wire from the ground harness back to the trailer wiring connector.

expert reply by: Jameson C