Whether you have a travel trailer or one that just carries cargo, adding electric brakes to it will give you quicker stopping power and control. Properly wiring the trailer’s electric brakes is critical but not difficult. The color of the wires is what they will usually be, but occasionally the color scheme will be different.
Installing a seven-way flat blade RV connector:
1.) Cut-off the trailer four-pin electrical connector and strip 1/4 inch of insulation from each wire.The seven-way flat blade RV connector plug has six flat blade connectors arranged in a circular pattern with one circular connector in the middle of the plug.If you look at the flat blade trailer connector from the distant end, the end that plugs into the tow vehicle, it has two flat connectors on top when the flange is facing up, two on the bottom, one on the left side and one on the right side.
Connect the existing trailer wires and the new brake wires using this color code:
Top left: black wire, 12-volt battery power.
Top right: brown wire, tail and running lights.
Left: green wire, right turn and stop lights.
Right: yellow wire, left turn and stop lights.
Bottom left: blue wire, brake controller wire.
Bottom right: white wire, ground wire.
2.) Run a piece of 10/2-gauge brake wire from the left wheel to the right wheel along the trailer axle. Attach the wire to the axle with zip ties.
3.) Run 10/2 brake wire from the trailer connector to the right wheel brake backing plate along the frame. Attach the brake wire to the trailer frame with wire clips.
4.) Connect the black 10/2 wire coming from the trailer plug to one of the right wheel wires. It does not matter which one; they are not polarized. Connect the white 10/2 wire to the other right wheel wire using 10-gauge solderless connectors.
5.) Connect the black 10/2 wire zip-tied to the trailer axle to one of the left wheel wires. It does not matter which one; they are not polarized. Connect the white 10/2 wire to the other left wheel wire using 10-gauge solderless connectors.
6.) Splice the black brake wire from the left wheel to the right wheel black brake wire using 10-gauge Scotch-locks.
7.) Splice the white brake wire from the left wheel to the right wheel’s white brake wire using 10-gauge Scotch-locks.
8.) Make a ground connection. Drill a 1/4-inch hole in the trailer frame tongue. Scrape the paint off a 1-inch diameter area around the hole on one side of the frame. Coat the scraped area with dielectric grease to keep corrosion away. Install a 1/4-inch by 1-inch galvanized bolt with a galvanized washer and lock washer on the scraped and greased side of the trailer frame.
9.) Connect a 10-gauge white wire from the trailer ground connector to the frame grounding bolt. Attach the wire to the bolt with a solder less 10-gauge eye connector.
10.) Connect the 10/2 white wire coming from the wheel brakes to the grounding bolt using a solderless 10-gauge eye wire connector. Coat the grounding bolt and connectors with dielectric grease to prevent corrosion.
11.) Connect the 10/2 black wire coming from the wheel brakes to the bottom left blue wire, brake controller wire on the seven-way flat blade RV connector plug.
12.) Install a breakaway battery box to the trailer tongue. Install the breakaway switch to the trailer tongue.
13.) Connect the breakaway wires. Connect one of the blue wires from the breakaway switch to the black wire going to the trailer brakes. Connect the other blue wire from the breakaway switch to the blue wire of the battery box. Connect the white wire from the battery box to the grounding bolt on the trailer frame.
14.) Test the trailer brake connections. Hitch the trailer to the tow vehicle, connect the seven-way flat blade RV wire connector plug and activate the breakaway switch by pulling on the safety cable. Pull the trailer with the tow vehicle and see if the brakes apply. If there is a resistance to the tow vehicle, then the brakes are working. Release the breakaway switch and apply the vehicle brake controller while driving. The trailer brakes should apply proportional to the amount of pressure you apply to the brake controller.