How to replace the capacitor in an electric furnace

Is your electric furnace blowing cold air, making odd noises, or not starting up? Chances are, a faulty capacitor is to blame. Replacing this part is easier than you think and it could save you a big repair bill! We’ll show you how to test and replace the capacitor in your electric furnace so you can stay cozy.

Notice: The guidance provided in this article is general and may not fully apply to your specific appliance model. While we aim to offer valuable advice for a variety of DIY appliance repairs, variations in models and configurations may result in differences in troubleshooting procedures, error codes, or part replacement requirements. For precise and accurate assistance, we recommend consulting the technical sheet or user manual for your appliance model.

Signs you need to replace the capacitor

The capacitor stores energy to start the blower motor and keeps it running smoothly, so if it’s failing, it can lead to a variety of problems. Here are some common signs that it might be time to replace the capacitor:

• Blower motor doesn’t start: The most obvious sign of a faulty capacitor is if the blower motor is slow to start or doesn’t start at all. If you hear a humming or buzzing noise but the motor isn’t running, the capacitor might not be providing enough energy to get it going.
• Furnace runs intermittently: If your furnace seems to be turning on and off frequently without completing a full heating cycle, it could be because the capacitor isn’t providing the right charge to keep the blower motor running.
• Unusual noises: A buzzing or humming sound coming from your furnace can indicate that the motor is trying to start but the capacitor isn’t doing its job.
• Furnace not blowing air: If the furnace is heating but there’s no airflow from the vents, the capacitor might be failing to start the blower motor.

If you’re experiencing any of these symptoms, it’s a good idea to test the capacitor and consider replacing it if necessary.

Safety precautions   

Safety should always be a priority when working on any appliance. Here are a few practical tips to help you stay safe:

• Turn off the power to the appliance by unplugging it or switching off the circuit breaker before starting any maintenance or repairs. This protects you from the risk of electric shock.
• Wear insulated gloves to shield your hands from sharp edges, pinching hazards, or debris.
• Work at a steady pace and take your time to avoid accidents or injuries.
• Make sure your workspace is well-lit so you can clearly see and access the parts you’re working on.
• Keep the area clear of clutter, and ensure children and pets stay out of the workspace.
• Never handle internal parts with wet hands. Check that both your hands and the work area are completely dry.
• Refer to your appliance’s user manual for any specific instructions or safety guidelines related to the part or repair.
• Handle parts gently to avoid damage to the appliance or potential injuries from applying too much force.
• Use safety glasses when dealing with chemicals, dust, or large debris to protect your eyes from harm.
• If the appliance was recently used, give it enough time to cool down before working on any heated components.
• Take photos or notes of wiring connections and terminals before disconnecting anything to make reassembly easier.
• Avoid touching exposed wires or terminals. If you must handle wires, use non-conductive tools or wear insulated gloves to minimize the risk of electrical shock.

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Tools and materials you’ll need

Before you begin replacing the capacitor in your electric furnace, it’s important to gather all the necessary tools and materials. Here’s a list of what you’ll need to complete the job:

• Screwdriver: A screwdriver will be needed to remove the furnace access panel and unscrew any fasteners holding the capacitor in place. Make sure to use the correct type (Phillips or flat-head) based on the screws in your furnace.
• Wrenches or pliers: These will help you disconnect the wires from the capacitor terminals. You might need these tools to gently pull the wires off.
• Multimeter: A multimeter is useful for testing the capacitor before you remove it. It can help confirm that the capacitor is faulty and needs replacing. You can also use the multimeter to test for voltage or continuity in other electrical components.
• Replacement capacitor: Be sure to have the correct replacement capacitor for your furnace. The specifications (voltage and capacitance) are typically listed on the old capacitor or in the furnace’s manual.
• Camera or notebook (optional): It’s a good idea to take a photo or write down the wiring connections before you disconnect anything. This ensures that you can easily reconnect the new capacitor in the same way as the old one.

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Replacement steps

Step 1: Disassembly and removal

1. Start by removing the access panel to expose the furnace’s internal components. You may need to unscrew or unclip the panel, depending on your furnace model.
2. The capacitor is typically found near the blower motor. It will either be attached to the blower housing or mounted on a bracket. It looks like a cylindrical metal can or a small rectangular box with two or more electrical terminals.
3. Carefully disconnect the wires attached to the terminals of the capacitor. It’s a good idea to take a photo or note down the wire connections so you can easily reconnect the new capacitor later.
4. Use pliers or a wrench to gently pull off the wires, being careful not to damage the terminals or surrounding components.
5. The capacitor may be secured with screws or clips. Use a screwdriver or wrench to loosen any fasteners holding the capacitor in place. 
6. Once loosened, remove the old capacitor from its mounting position.

Step 2: Installation and reassembly

1. Take the new capacitor and position it in the same place as the old one. Make sure it matches the specifications (voltage and capacitance) of the old capacitor to ensure compatibility.
2. If the new capacitor comes with a bracket, attach it securely to the furnace. Otherwise, mount the capacitor using the original mounting hardware.
3. Using the photo or notes from earlier, reconnect the wires to the correct terminals on the new capacitor. Make sure the connections are tight and secure to avoid any loose connections that could cause problems later.
4. Once the capacitor is installed and the wires are connected, carefully replace the access panel. Secure the panel with screws or clips to ensure everything is properly enclosed and protected.
5. Before powering the furnace back on, do a quick check to ensure that the capacitor is properly installed, the wires are securely connected, and there are no loose parts or tools inside the furnace.

Read more: 12 simple space heater safety tips for this winter

Additional information

Thanks for reading! We hope this guide helped you replace the capacitor on your electric furnace. 

If you still need some replacement parts, grab your model number and head over to AppliancePartsPros.com. We offer over two million parts and most orders arrive in two business days. If you need some help with finding the right part or placing an order, you can contact our team at 1 (877) 477-7278.

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