The connection between a tow vehicle is made via a four- or seven-conductor cable, depending upon the complexity of the trailer's electrical systems. In order for the trailer to be conveniently separated from the tow vehicle, and also towed by any properly equipped tow vehicle, the cable from the trailer is terminated in a plug, and the harness of the tow vehicle is terminated in a matched receiver. Seven blade trailer plugs are round, and wired in an industry-standard combination of terminal numbers mated to color-coded wires.
Use a screwdriver to release the fastener holding the case of the plug to the inner terminal hub. Remove the case and slide it, small end first, over the seven-conductor cable from the trailer's wiring harness. Use a craft knife to separate two inches of the cable's outer sleeve from the inner wires, being careful not to damage any of the color-coded insulation.
Use wire strippers to detach 1/2-inch of insulation from each separate wire, and twist the bared strands of each wire between finger and thumb until seven tight, rope-like braids have been created. One at a time, install the bared wire into a hole in the top of a terminal then use a screwdriver to tighten down the securing screw in the top of the terminal.
Read the terminal numbers molded into the material of the hub, one beside each securing screw, and attach each wire to it's proper terminal in the following combinations: terminal one, white; terminal two, blue; terminal three, brown; terminal four, black; terminal five, yellow; terminal six, green and terminal seven, purple (in the center).
Slide the case back up the cable until it is seated fully on the terminal hub, engaging an orientation tooth in its matching slot if such is molded into the two pieces, then reinstall the fastener.
