Box fans provide a convenient way to circulate air in areas where the air from a fixed-location fan will not reach. Many box fans take advantage of a three-speed motor. Adjusting a fan's speed allows the fan to circulate the air in different-sized rooms without producing an overpowering blast of air. Upgrading a single-speed fan to a three-speed fan requires a new switch and motor. Single-speed box fans use parts with two wires, while a three-speed box fan needs a four-wire switch and motor.

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Three-speed box fans uses four wires to control its speed.

Step 1

Identify the three-speed switch's and fan motor's wires, using their wiring diagrams as a guide. The switch contains one input wire, often called "Line", and three-speed wires. The motor contains three-speed wires and a neutral wire. Each wire uses its own color-coded insulation, and the colors vary between manufacturers.

Step 2

Strip one half-inch from the end of each wire with wire strippers. This includes the wire set that enters the fan. It has a wall plug on the other end.

Step 3

Twist the end of the motor's neutral wire to one of the wires from the wire set that enters the box fan. Secure them with a wire nut. The wire set that enters the fan contains two wires.

Step 4

Twist the second wire from the wire set that enters the fan to the switch's input wire. Secure them with a wire nut.

Step 5

Twist the fan's low-speed wire to the switch's low-speed wire. Use the wiring diagrams on the motor and switch as a guide. Secure these wires with a wire nut.

Step 6

Twist the fan's medium-speed wire to the switch's medium-speed wire. Use the wiring diagrams on the motor and switch as a guide. Secure the wires with a wire nut.

Step 7

Twist the fan's high-speed wire to the switch's high-speed wire. Use the wiring diagrams on the motor and switch as a guide. Secure the wires with a wire nut.

Step 8

Route the wires away from the fan blades. Secure the wires to the box fan's frame with plastic wire ties.