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Troubleshooting Trailer Surge Brakes That Activate in Reverse with New Truck


2018 f150 First time pulling a trailer with surge brakes and r locking in reverse. the trailer works fine with my other truck 2012 f150 please help.


Expert Reply:

A surge coupler/actuator will activate the brakes on the trailer unless it has a lockout feature, either a manual lockout as with coupler # T63FR or an electric lockout as on part # T4854020. Since the same trailer backs up without any problem using your other truck, the 2012 F-150, most likely that truck has a reverse light circuit present on the trailer wiring to deliver a lockout signal for the coupler's solenoid.

If your new truck has only a 4-pole wiring setup then you'll just need to add an adapter # 20036 which lets you add an additional circuit to carry the truck's reverse light signal to operate the lockout. This adapter has one wire that splices into the reverse light wiring on the truck.

If the new truck and trailer have a 7-way wiring setup (which includes a reverse light signal) then there may be an issue on that one circuit. Please refer to the linked photo to see how the pins on a 7-way are configured; the reverse light signal is carried on the center pin. If you have a tester like # PTW2992 you can test the reverse light circuit on the truck's wiring connector to make sure the signal is present when the truck is in reverse gear. Be sure to have a competent helper to assist since you'll need to test the connector while the truck is in reverse.

Please feel free to tell me a bit more about the type of wiring on each truck and whether the coupler has an electric or manual type lockout. If it is a manual/mechanical lockout the problem could be due to damage to that feature on the coupler.

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