How to Replace a Furnace or A/C Capacitor

Introduction

This tutorial will guide you through the process of replacing a furnace or air conditioning capacitor. Capacitors are essential components that help run your HVAC system efficiently. Understanding how to replace them can save you time and money, especially during peak usage in hot weather.

Step 1: Understand the Types of Capacitors

• Run Capacitor: Used to operate a motor.
• Dual Run Capacitor: Combines two run capacitors into one, typically labeled with:
  • Herm: For the compressor.
  • Fan: For the fan motor.
  • C: Common or neutral.

Tip

Always check the capacitor’s microfarad rating (MFD or UF) and voltage. The larger number is for the compressor, while the smaller is for the fan.

Step 2: Gather Necessary Tools and Parts

• Screwdriver (5/16 or 1/4 inch)
• Multimeter (to check capacitor function)
• New capacitor (ensure it matches the specifications of the old one)
• Safety gloves and goggles

Step 3: Disconnect Power

• Locate the power disconnect, usually near the outdoor unit.
• Open the disconnect cover and pull out the plug or switch off the circuit breaker.
• Use a voltage meter to confirm there is no power before proceeding.

Step 4: Access the Capacitor

• Remove the access panel of the air conditioner or furnace where the capacitor is located.
• Unscrew the panel using the appropriate screwdriver.

Step 5: Remove the Old Capacitor

• Identify the capacitor and note the wiring configuration.
• Discharge the Capacitor: Use a screwdriver to short the terminals (common to herm, and common to fan) to safely discharge any stored energy.
• Remove the wires from the old capacitor one at a time, or take a picture for reference.
• Unscrew the capacitor from its mounting bracket.

Step 6: Install the New Capacitor

• Position the new capacitor in the bracket.
• Reconnect the wires to the new capacitor terminals:
  • Herm: Larger rating
  • Fan: Smaller rating
  • C: Common
• Ensure all connections are secure.

Tip

If connectors are brittle or damaged, replace them to prevent future issues.

Step 7: Reassemble and Restore Power

• Reattach the access panel and secure it with screws.
• Restore power by plugging the disconnect back in or turning on the circuit breaker.
• Check the system to ensure it operates correctly.

Step 8: Check Capacitor Functionality

• Use a multimeter set to measure capacitance.
• Test the old and new capacitors to confirm the microfarad ratings match their specifications.

Conclusion

Replacing a capacitor can be a straightforward task if done safely and correctly. Always ensure to check the ratings of the new capacitor match the old one. For future maintenance, consider having spare capacitors on hand, especially during periods of extreme heat. For any issues, consult a professional HVAC technician.