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How to Wire a 4-Speed Blower Motor

William Kinsey

A 4-speed blower motor is a device commonly found in the HVAC (heating, ventilation and air conditioning) industry. These blower motors are used in electric heat furnaces and some air conditioning units. These motors use multiple internal coils to provide multiple fan speeds. This is why these units have many wires. There is one common wire which all of the coils share and then there are the individual hot wires. Energize the common wire and one of the individual wires and the motor will operate at a certain speed. If you choose a different individual wire, the speed will change.

Wire a 4-Speed Blower Motor
  1. Shut off the power to the HVAC unit at the main power panel. Check the manufacturer's wiring manual to verify blower motor wiring configuration and what size control switch should be used with it. Locate the black and white wires that will supply power to the motor.

  2. Connect the white wire to the common wire on the motor. Secure it with plastic twist caps. Connect the black hot wire to the hot terminal of the speed controller. Use the instructions that come with the speed controller to identify speed terminals 1 through 4.

  3. Connect speed terminal 1 to the low speed wire of the motor. Connect speed terminal 2 to the medium low speed wire of the motor. Connect speed terminal 3 to the medium high speed wire, and connect speed terminal 4 to the high speed wire of the motor. Cover any splices with plastic twist caps. Some motors have two high speed wires that are connected together by a capacitor. Only connect to one of the two high speed wires.

  4. Turn the power back on and test the motor by turning it on and taking it through all four speeds.