Wiring a Blower Motor

Blower motors are used in many air-conditioning and central heating systems to push air through the duct system. The speed wires inside the blower’s motor are connected to a fan relay. A run capacitor will maintain a constant voltage supply across the blower motor’s secondary windings. A motor with missing or malfunctioning capacitors will stop when the motor’s rotor reaches a weak spot on the windings. You need to make sure that the replacement for the blower motor’s ratings suits the old motor’s speed ratings, voltage, horsepower and amperage. Here are the steps on how to wire it.

You will need:

  1. Needle-nose pliers

Blower Motor


  1. First, check the motor’s housing that locates the blower motor’s wire identification label. The wire identification label gives each wire’s its function and insulation color.
  2. Search the wiring diagram of the unit that holds the blower motor. The wiring diagram identifies the fan relay or multi-speed motor. The blower speed terminals use identification labels such as “High”, “Medium” and “Low”.
  3. Then, press the blower motor’s capacitor wires or the brown wire onto the capacitor’s wire terminals with needle-nose pliers.
  4. A blower motor’s capacitor is like an oval metal cylinder or round-shaped housings that mount on the outside of the blower’s housings. Two sets of wire terminals extend from the top of the capacitor. Place a single blower motor capacitor wire onto each terminal by pressing it.
  5. Next, follow the wires that enter the unit from the power source. These wires connect to a two-sided terminal block as the black colored insulation lead from the side of the terminal block to the fan relay and the hot side of all other electrical parts.
  6. All of the common wires especially the white-colored insulation placed in the other side of the terminal block.
  7. Search the blower motor’s common wire, which has the white-colored insulation. Press the wire connector onto the terminal block’s common side using needle-nose pliers.
  8. Press the blower motor’s speed wires onto their respective fan relay terminals. Press the remaining wire of the single-speed blower motor onto the only empty fan relay terminal.
  9. Then, press a multi-speed blower motor’s “High” speed wire, which is the black-colored insulation onto the fan relay’s terminal marked “High”. Press a multi-speed motor’s “Medium” or “Med” speed wire or the blue/yellow colored insulation onto the fan relay’s terminal marked with “Medium” or “Med”. Press the red-colored insulation or the multi-speed motor’s “Low” speed wire onto the fan relay’s terminal marked with “Low”.

Image Credit:

Flickr CC

Additional Reading:

Forced Hot Air Furnaces : Troubleshooting and Repair

How Your House Works: A Visual Guide to Understanding & Maintaining Your Home