Trailer brakes are required for tow vehicles that have a gross vehicle weight rating, or GVWR, of more than 3000 pounds. These brakes are vital, as the tow vehicle breaks may not be sufficient to stop the loaded vehicle. Trailer brakes can also help with handling and with reducing trailer sway while in motion. Electric trailer brakes use electromagnets to actuate the drum brakes, so an electric break controller must be installed in the cabin of the tow vehicle to set up and control the electric trailer brakes.
Read the owners manual for your tow vehicle. Most RVs, SUVs, trucks and vans made after the mid nineties, and which have a Class III or better towing hitch, will have a quick plug located under the dashboard or a pigtail connector in the glove box. If you can find the plug in your vehicle, simply plug in the trail brake controller and connect the other end of the wiring at the hitch and trailer.
Find the brake light switch in cases were you do not have a preset plug in on your vehicle. From the brake light switch, which will be attached to the brake pedal or in the engine bay, four wires will need to be run and connected to the back of your vehicle.
Connect the trailer feed wire. This is typically the blue wire on the connector. Many vehicles with factory tow packages installed will have this wire already. If not, a wire the wire must be run under the vehicle, through the firewall, and come out at the brake control mounting location. Some vehicles may come with holes through the firewall that have grommets to run the wire through, if not a hole must be drilled. Use a steel drill bit. Once the hole is created use paint on the edges to avoid corrosion. Place a rubber grommet into the hole to reduce friction on the wire.
Connect the ground wire, which is usually white. It can be connected to any safe ground location on the tow vehicle.
Run the brake switch, which is usually red. The brake switch can be found at the top of the brake pedal. Using a circuit tester find out which of the wires have power when the brake is pressed. Tap into this wire using a scotch lock. Scotch locks can be purchased at most hardware stores. Associates will be able to find the exact ones for your needs.
Attach the battery power wire, which is usually black. Like the trailer wire, your vehicle may already have this run through and attached at the back. If not, a new wire can be run through the hole that was drilled for the trailer wire or a new one can be created as in step 3.
Caulk the drilled holes to reduce their exposure to water for the run wires.
