Towing a heavy trailer would put undue stress and wear on the brakes of the Ford F-250 without an electronic brake controller. A controller activates the electric trailer brakes each time you apply the brake pedal in the Ford. Fortunately, Ford assumed most F-250 owners would tow a trailer sooner or later and equipped its trucks with a factory brake controller wiring harness, making for quick electrical connections when installing a controller.
Find the plastic access panel under the dashboard on the driver's side. Twist its four screws in a counterclockwise direction with a flat blade screwdriver. Lower the panel and place it aside.
Find the light gray plastic wiring port just beneath the steering column or next to the firewall near the accelerator pedal. Push the connector of the brake-controller adapter pigtail -- available from the brake controller manufacturer -- into the truck's wiring port until it clicks into place.
Hold the mounting bracket for the brake controller to the flat area on the underside of the dashboard where the driver will have easy access to it, but will not be in the way. Use the bracket as a template and mark the underside of the dashboard through the mounting holes on the bracket with a felt-tipped pen. Place the bracket aside.
Drill through the pen marks with a 1/8 inch drill bit installed into a power drill. Use care not to damage any wires or hoses on the opposite side of the dashboard when drilling. Hold the bracket into position and drive in the retaining screws through the bracket and into the underside of the dashboard with a Phillips screwdriver.
Place the brake controller into the bracket and tighten the retaining screws finger-tight. Rotate the controller so that it can it is easily seen from the driver's seat. Tighten the retaining screws with a Phillips screwdriver.
Push the connector on the opposite end of the brake-controller adapter pigtail into the port on the brake controller until fully seated. Use cable ties to secure any excess length of cable hanging down to a dashboard structural member. Replace the plastic trim panel and twist the four screw heads in a clockwise direction to lock the panel in place.
Push the trailer wiring connector into the rear trailer-towing receptacle just under the rear bumper on the truck. Calibrate or test the controller as per the manufacturer's instructions before towing a trailer.
