Why Would Trailer with Surge Brakes Work Allow Reversing for a While Then Stop

Question:

I have a boat trailer that is giving me issues, however I am wondering now if it is my truck. When I put my truck in reverse, the disc brakes lock up and i am stuck. The only way I can back up now is with a lockout key. It had been working for 2 years, so something happened. Could this be a bad fuse? corroded wiring under the truck? something else? What makes this head scratching is I had this happen in my 2007 f150, and started by replacing the 7 way trailer connector.. it worked! Now, with my 2018 F150, I replaced the connector and still have the issue this time around. Please help! I brought it to a trailer shop and they did everything they could with the trailer itself- still no luck.

asked by: Joe P

Expert Reply:

If the trailer with surge brakes used to let you back up but now it's not that would indicate it has an electric reverse lockout solenoid that is currently not working. This could be a blown reverse light trailer wiring fuse, bad wiring, dirty trailer wiring connectors, bad wiring on the trailer to the solenoid, or a bad solenoid itself.

Since a trailer shop looked at it that would indicate it's probably a blown fuse or bad wiring/corrosion that is at fault.

expert reply by: Jameson C