Adding a 7-Way Trailer Connector to a 2005 Ford Expedition with Factory 4-Way

Question:

Is the wire for the 12 volt for the trailer hidden somewhere or do I need to run it under the vehicle. Also will I need to install a relay or other parts for the 12 volt wire to function properly. The blue brake controller wire is at the 4 way plug hanging.

asked by: Ray

Expert Reply:

On a 2005 Ford Expedition with a factory 4-Way, the wires for the brake and 12-volt circuits are actually ran to almost the back of the vehicle. If you follow your 4-Way forward under the vehicle it should run into another harness. This connection point has more wires going into it than coming out to go to the 4-Way. If you expose the wires on this forward harness, then you will be able to test them to find the 12-volt circuit. The orange wire should be the 12-volt power wire. But use a circuit tester like # PTW2993 to test to be sure.

Only if that wire is not there would you have to add wire to run to the battery via a 40-amp circuit breaker # PK54540. I have included a link to an FAQ article that should help you. For a 7-Way use # 37185.

expert reply by: Michael H