What Causes a Trailer With Surge Brakes To Lockup While In Reverse

Updated 07/26/2020 | Published 06/26/2019

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Question:

I have a friend whose surge brakes engage when backing up. normal He has a 2012 F150 with a 4-wire flat connector. The truck does not recognize the trailer when connected. When he connects said trailer to his fathers 2018 F150 with the same four wire flat connector, it recognizes the truck and the brakes dont engage when backing up. Both vehicles have the flat four next to the 7 blade recepticle on the Tow vehicle. Blue wire to reverse bulb splice? Defective/incorrect receptical? Your advice would be appreciated. Thank you,.

asked by: Mark G

Expert Reply:

The issue your friend is having with his trailer is a mechanical one so we can rule the vehicle out. The reasoning for this is because the only way you would have been able to back up the trailer with using just a 4-way trailer connector is if you either physically applied a manual lockout or the trailer had free backing braking assemblies. Surely you would know whether or not the manual lockout was used or not so that leads me to think you have free backing braking assemblies. The free backing braking assemblies will grab when you first go to back up but will then release so you might just need to get past the initial grab.

If the above is not the case then and you have none of items needed to disengage the brakes while in reverse then the reason that they did not lock up with the 2018 Ford F-150 is because there was not enough pressure applied to the coupler for the master cylinder to open. If this is the case than a easy fix for you to be able to disengage the brakes while in reverse is to add an electric lockout part # T4748800 with 4 to 5-way adapter part # C57187.

expert reply by: Conner L