How Should I Connect a New Cooker Extractor Motor?

Replacing the motor in a cooker extractor hood is a common repair that can save hundreds of dollars compared to replacing the entire appliance. However, kitchen fan motors are specialized; they often feature multiple speeds and external capacitors. Whether you are installing an OEM replacement or a universal centrifugal fan motor, correct wiring is essential for fire safety and to prevent burning out the new windings. Here is the professional approach to connecting a new extractor motor.

1. Identify the Wiring Color Code

Cooker hoods sold globally follow different electrical standards. Before connecting, identify your wiring scheme:

• UK/Europe (BS 7671): Brown (Live), Blue (Neutral), and Green/Yellow (Earth/Ground).
• North America (NEC): Black (Hot), White (Neutral), and Green or Bare Copper (Ground).
• The Speed Wires: Most motors have additional wires for speed control (Low, Medium, High). These are often Red, White, and Black (on the motor side) or connected to a numbered terminal block (1, 2, 3).

2. Connecting the Start Capacitor

Most induction-style extractor motors require a start/run capacitor (usually 2µF to 6µF).

• Integrated vs. External: If the new motor has two dedicated wires (often same color, like two Greys or two Whites) separate from the main harness, these must be connected to the terminals of the capacitor.
• Why it matters: Without the capacitor, the motor will hum but won't spin, or it may spin in the wrong direction and overheat within seconds.

3. Wiring for Multi-Speed Control

The extractor switch on your hood acts as a selector. It sends the "Live" voltage to one of several "taps" on the motor windings.

1. The Common Wire: Connect the Neutral (Blue/White) directly to the motor’s common lead.
2. The Speed Leads: Connect the wires from the selector switch to the corresponding speed leads on the motor.
   • Low: Highest resistance winding.
   • High: Lowest resistance winding.
3. Testing Resistance: If the wires aren't labeled, use a multimeter set to Ohms. The pair with the highest resistance is usually the "Low" speed setting.

4. Proper Earthing and Mechanical Safety

Because the cooker hood is a metal appliance located near water and heat, Earth bonding is non-negotiable.

• Ensure the Green/Yellow (or Green) wire is securely fastened to the motor housing or the metal chassis of the hood.
• Use heat-shrink tubing or high-quality crimp connectors. Avoid standard "twist-on" wire nuts if the motor is located directly in the path of hot, greasy airflow, as the plastic can degrade over time.

5. Airflow Orientation (CW vs. CCW)

Before finalizing the mount, verify the rotation direction. Some universal motors are reversible by swapping the capacitor leads.

• An extractor must pull air up and out. If the motor is spinning the wrong way, it will simply swirl the steam around your kitchen.
• Check the arrow on the motor casing indicating CW (Clockwise) or CCW (Counter-Clockwise) rotation.

6. Post-Installation Testing

Once connected, perform a "Step-Up" test:

• Turn on the light first to ensure the board has power.
• Start the fan on Speed 1 (Low). Listen for grinding or humming.
• Switch through all speeds to ensure the switch logic matches the motor windings.
• Check the external vent flap to ensure it is opening under the air pressure.

Conclusion

Connecting a new cooker extractor motor requires careful identification of the common neutral, the speed taps, and the start capacitor. While the color codes may vary between manufacturers, the electrical logic remains the same: the switch directs power to different parts of the motor coil to change the fan's RPM. If your new motor has more wires than your old one, consult the included wiring diagram to identify the "Park" or "Auto" wires often used in modern sensor-driven hoods.