Wiring 7-Way Trailer Connector After Installing OEM Brake Controller in 2014 Ford F150

Question:

I installed the OEM controller in the dash. Wiring was stored where it should have been. I located the aft trailer wiring harness above the spare tire and plugged in the OEM 7 and 4 pole socket. However I noticed the truck wiring harness side of the plug only has the wires for the 4 pole plug. I could not locate the blue controller wire or backup light and battery charge wire. I checked the fuse box under the engine hood and it has all the fuses and relays needed for the controller. My question is, can I splice a blue wire to the one coming out of the controller and run it back to the 7 pin connector. I haven’t went to the dealer yet to get the controller unlocked and flashed, until I get the blue wire issue fixed. I’m not concerned with the backup lite and battery charge wire going to the trailer.

asked by: Terry

Helpful Expert Reply:

If by 'OEM Socket', you mean something like the # HM40975, you'll need to obtain a new harness from Ford to connect the trailer connector to the connector on the driver's side frame rail. You'll be all plug and play from there.

If you're speaking of an adapter like # 37185, you can certainly run your own circuit from the blue brake controller wire if need be, but you might not have to. Go to that connector that you plugged your OEM trailer connector and follow it to the junction which should be on the driver's side frame rail. Find the wiring harness entering that junction from the front of the vehicle and look for an orange and a dark blue wire. The orange carries the constant 12-volt from the battery, the dark blue carries the output from the brake controller. The reverse lamp circuit should be there too, but you'll need to circuit test the remaining wires to see which lights up with the transmission in reverse. Once you locate the three circuits, tap into the harness and run each circuit to the trailer connector.

expert reply by: Mike L