Air Flow Gurus

Troubleshooting Furnace Problems: Capacitors and DIY Fixes

Is your furnace acting up again? It’s a common problem that many homeowners face, but fear not! In this article, we’ll take a closer look at some of the most common furnace problems and how you can address them.

We’ll also delve into the world of capacitors and their role in your furnace’s blower motor. So grab a cup of coffee, sit back, and get ready to learn everything you need to know about furnace problems and capacitors.

Common Furnace Problems

Common Furnace Problems

– Is your furnace not turning on? Is it making strange noises?

These are common furnace problems that many people experience. But what exactly causes them?

– One common issue is a malfunctioning thermostat. If your furnace isn’t turning on, it could be due to a problem with the thermostat.

Check if the thermostat is set to the correct temperature and ensure that it’s working properly. – Another common problem is a dirty air filter.

When the air filter gets clogged with dirt and debris, it restricts airflow and can cause your furnace to work inefficiently. Make sure to clean or replace the filter regularly.

– Ignition problems are also common. If your furnace is not igniting, it could be due to a faulty pilot light or an issue with the ignition control.

In this case, it’s best to call a professional to diagnose and fix the problem.

Capacitor and Blower Motor

– Now let’s talk about capacitors and their role in your furnace’s blower motor. A capacitor is an electrical component that stores and releases energy.

In a furnace, capacitors are responsible for providing the necessary power to start and run the blower motor. – There are different types of capacitors used in furnaces, such as start capacitors, run capacitors, and dual run capacitors.

Start capacitors provide the initial boost of power to start the motor, while run capacitors continue to provide energy to keep the motor running smoothly. – If your furnace’s blower motor is not working properly, it could be due to a faulty capacitor.

A capacitor can become weak or fail over time, which can lead to issues with the blower motor. If you suspect a capacitor problem, it’s essential to have it checked and replaced if necessary by a professional technician.

DIY Repairs and Quick Fixes

Types of Capacitors

– Now that we’ve covered the basics of capacitors, let’s dive deeper into the different types. Start capacitors are designed to provide a high amount of power for a short period, while run capacitors deliver a continuous supply of power to keep the motor running smoothly.

– Dual run capacitors, as the name suggests, combine the functionality of both start and run capacitors. They are commonly used in HVAC systems with two motors, such as those found in heat pumps.

– It’s important to note that working with capacitors can be dangerous if you’re not familiar with electrical systems. If you’re unsure about any DIY repairs, it’s always best to consult a professional to avoid any potential hazards.

DIY Repair Ratings and Quick Fixes

– Wondering if you can tackle furnace problems yourself? Well, the difficulty level of DIY repairs can vary depending on the problem at hand.

Let’s take a look at some DIY repair ratings to help you determine whether the fix is easy or best left to the professionals. – Easy fixes, such as replacing an air filter or reprogramming a thermostat, can be done by most homeowners with minimal tools and experience.

These repairs typically don’t require extensive knowledge or technical skills. – Quick fixes, on the other hand, may require a bit more expertise.

For example, replacing a faulty capacitor or cleaning the blower motor might require some electrical knowledge and specialized tools. If you feel confident in your abilities, you can give it a shot, but don’t hesitate to call a professional if you’re unsure.


In conclusion, furnace problems can be a hassle, but with a little knowledge and the right approach, you can address them effectively. Remember to check common issues like the thermostat and air filter before diving into more complex problems like capacitors.

And if you’re not comfortable with DIY repairs or unsure about the severity of the issue, it’s always best to consult a professional. A well-maintained furnace will keep you warm and cozy during those chilly winter months, so take the time to keep it in top shape.

Stay informed, stay warm!

Symptoms of a Bad Capacitor

Symptoms of a Bad Capacitor

One of the most common signs of a bad capacitor in your furnace is when you hear the blower humming, but no air is blowing through the grates. This humming noise indicates that the motor is trying to start but is unable to due to a lack of power.

Without a functioning capacitor, the blower motor won’t receive the necessary electrical boost to start the airflow. Another symptom of a bad capacitor is a loud hum or buzzing noise coming from the furnace.

This noise may indicate that the capacitor is no longer able to provide a steady flow of energy, causing the motor to struggle or vibrate. If you notice any of these symptoms, it’s essential to act promptly to avoid further damage to your furnace.

Troubleshooting a Bad Capacitor

Diagnosing a bad capacitor requires some troubleshooting to ensure that it is indeed the culprit causing your furnace issues. Before starting any troubleshooting, make sure to turn off the power to avoid any potential electrical hazards.

Firstly, check the furnace voltage to ensure it is receiving the correct amount of power. Insufficient voltage can cause the capacitor to fail prematurely.

If the voltage is incorrect, contact a professional to address the electrical issue. Once you’ve verified the voltage, it’s time to focus on the capacitor.

Keep in mind that capacitors store electrical energy even when power is disconnected, so the next step is to discharge the capacitor. You can do this by using an insulated screwdriver to short across the terminals, ensuring proper safety precautions.

After discharging the capacitor, you can proceed with testing it. Remove the capacitor from the furnace and visually inspect it for any signs of bulging or leaking.

These are clear indications of a failed capacitor that needs to be replaced. To further confirm the capacitor’s functionality, you can use a multimeter to test its capacitance and resistance.

Set the multimeter to the capacitance mode and connect the leads to the capacitor terminals. The reading should be within the manufacturer’s specified range.

For resistance testing, set the multimeter to the resistance mode and check for continuity across the capacitor terminals. If there is continuity, it means the capacitor is faulty and needs to be replaced.

Approaches to Diagnose and Repair

Calling a Furnace Company

If you’re not comfortable with troubleshooting or if the issue seems more complex, it’s best to call a furnace company for assistance. Experienced technicians have the expertise to diagnose and repair furnace problems, including those related to capacitors.

They have the necessary tools and knowledge to test capacitors accurately, ensuring a reliable diagnosis and repair.

Testing the Capacitor

If you feel confident in your abilities and decide to tackle the repair yourself, the following steps will guide you through testing and replacing a faulty capacitor. 1.

Discharge the capacitor by following the steps mentioned earlier to ensure your safety. 2.

Remove the capacitor from the furnace, taking note of how it is wired. Make sure to disconnect any wires attached to it and label them for easy reconnection later.

3. With the capacitor in hand, test it using a multimeter as described earlier to verify if it is faulty or not.

4. If the capacitor is indeed faulty, it’s time to replace it.

Purchase a new capacitor with the same specifications as the old one. Capacitors are widely available at local home improvement stores or online.

5. Install the new capacitor into the furnace, reconnecting the wires exactly as they were on the old capacitor.

6. Once the new capacitor is securely installed, turn on the power and test the furnace to ensure the blower motor starts smoothly and distributes airflow correctly.

Remember, if at any point during the repair process you feel uncertain or uncomfortable, it is best to call a professional for assistance.


By understanding the symptoms of a bad capacitor and the troubleshooting steps involved, you can confidently diagnose and address issues with your furnace’s blower motor. Whether you choose to call a furnace company or tackle the repair yourself, prioritizing safety is crucial.

Regular maintenance and prompt attention to furnace problems will ensure that your heating system operates efficiently, keeping you warm and comfortable throughout the winter months.

Buying a Capacitor

Matching Ratings

When it comes to buying a new capacitor for your furnace, it’s crucial to ensure that you select one with matching ratings to the old capacitor. Capacitors have two important ratings: microfarad/microfarad (F) rating and voltage rating.

The microfarad rating represents the amount of electrical charge the capacitor can store. It’s essential to choose a capacitor with the same microfarad rating as the old one to ensure optimal performance.

Using a capacitor with a higher or lower microfarad rating can result in issues such as motor damage or reduced efficiency. The voltage rating refers to the maximum voltage the capacitor can handle safely.

Selecting a capacitor with a lower voltage rating than required can lead to premature failure, while choosing one with a higher voltage rating is acceptable and ensures durability. Consult your furnace’s manual or contact a professional technician to determine the exact capacitor specifications needed for your system.

By matching the microfarad/microfarad and voltage ratings, you can confidently purchase a suitable replacement.

Where to Buy a Capacitor

Once you know the correct specifications for your furnace capacitor, you have several options for purchasing a replacement. HVAC parts stores are a popular choice, as they specialize in heating and cooling components.

Local HVAC parts stores often carry a wide range of capacitors, allowing you to select the right one for your furnace. Online options are also available and provide convenience and access to a larger selection of capacitors.

Many reputable online retailers offer detailed product descriptions and customer reviews to help guide your purchase decision. Be sure to choose a reliable seller with positive reviews to ensure you receive a quality capacitor.

When considering the cost of a furnace capacitor, it’s important to factor in both the price of the capacitor itself and any additional fees related to installation.

Importance of Having a Spare Capacitor

Potential Need for Future Repairs

Having a spare capacitor on hand can be beneficial in case of future repairs. As with any mechanical component, capacitors can fail over time and require replacement.

By having a spare capacitor readily available, you can quickly address any issues that may arise, minimizing downtime and ensuring efficient operation of your furnace. Additionally, capacitors can sometimes fail unexpectedly, leaving you without heat during the colder months.

Having a spare capacitor allows you to replace it immediately and restore warmth to your home without delay.

Cost of Repair

When it comes to furnace repairs, it’s essential to consider the cost involved. Hiring a professional technician to diagnose and repair a faulty capacitor usually incurs a minimum fee for their time and expertise.

This fee typically covers the technician’s arrival and an initial assessment of the problem. If you have a spare capacitor, you can save on this minimum fee by replacing the faulty capacitor yourself.

This can be a cost-effective solution for those comfortable with DIY repairs. Another cost consideration is scheduling repairs during normal hours.

Furnace repairs often have higher rates for after-hours or emergency service calls. By having a spare capacitor at hand, you can perform the replacement during regular business hours, saving on potential additional charges.


Buying a replacement capacitor for your furnace involves understanding the importance of matching its ratings, including the microfarad/microfarad and voltage ratings. HVAC parts stores and online retailers provide convenient options for purchasing a replacement capacitor, ensuring you have the right component for your furnace.

Having a spare capacitor on hand can prove invaluable for future repairs and unexpected failures. By being prepared, you can minimize downtime and potentially save on service fees associated with professional repairs.

Remember, safety should always be a priority. If you’re uncertain about any repair or replacement procedure, it’s best to consult a professional technician to ensure proper installation and functionality of your furnace capacitor.

Popular Posts