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The Ultimate Guide to Buying and Replacing Your AC Capacitor: Everything You Need to Know

to an AC Capacitor: A Crucial Component of Your Cooling System

In the scorching heat of summer, our air conditioning units become our saving grace. Whether you have a traditional outside AC unit or a modern heat pump, there is an unsung hero working tirelessly to keep you cool – the AC capacitor.

This small cylindrical container is an essential part of your cooling system, providing the power and energy storage necessary for the smooth functioning of your condenser fan motor and compressor. In this article, we will delve into the world of AC capacitors, exploring their functions and buying options, so you can make an informed decision when the time comes to replace or upgrade this vital component.

What is an AC Capacitor? An AC capacitor, also known as a run capacitor or start capacitor, is a powerful energy storage device.

It is often found in the outdoor unit of air conditioners and heat pumps, playing a crucial role in their operation. Encased in a cylindrical container, these capacitors are capable of storing and releasing electrical energy as needed.

Functions of an AC Capacitor

The primary function of an AC capacitor is to supply power to your cooling system. When you turn on your air conditioner or heat pump, the capacitor provides a burst of electricity to jumpstart the motor.

This is especially important during startup, when the motor requires an extra jolt of power to get moving. Once the motor is running, the capacitor continues to supply the necessary power to keep it operating smoothly.

Another function of an AC capacitor is to ensure uninterrupted running of your cooling system. It acts as a bridge between the power supply and the motor, maintaining a steady flow of electricity.

Without a functioning capacitor, your condenser fan motor and compressor may experience frequent stops and starts, leading to inefficiency and potential damage to the motor. Additionally, an AC capacitor can provide that extra juice when needed.

During periods of peak demand or extreme heat, your cooling system may require more power to cool your home effectively. A capacitor with a higher capacitance rating can deliver the necessary surge of energy, ensuring optimal performance even in the toughest conditions.

Where to Buy AC Capacitors Online

If you’re in the market for a new AC capacitor, the internet offers a plethora of online buying options. With just a few clicks, you can explore a wide variety of capacitors and make a purchase from the comfort of your own home.

Here are some popular online retailers where you can find AC capacitors:

1. Online Retailer A: This reputable retailer specializes in HVAC parts and accessories.

They offer a user-friendly website with detailed product descriptions and clickable links for easy navigation. With a wide range of capacitors to choose from, you can find the perfect fit for your cooling system.

2. Online Retailer B: Known for their customer satisfaction and fast shipping, this online retailer has a vast selection of AC capacitors.

Their website features a convenient search function that allows you to filter products based on specific criteria, such as brand, voltage, capacitance, and more. With competitive prices and reliable service, they are a popular choice among homeowners and HVAC professionals alike.

Where to Buy AC Capacitors Locally

If you prefer the traditional route of purchasing from brick-and-mortar stores, there are several options available to you. Here are some places where you can find AC capacitors locally:


Local Parts Store: Many cities have parts stores that specialize in HVAC components. These stores are staffed by knowledgeable professionals who can assist you in finding the right capacitor for your cooling system.

They often carry a wide range of capacitors from various manufacturers, allowing you to compare and choose the best option that fits your needs. 2.

Home Improvement Stores: Home Depot, Lowe’s, and Menards are popular home improvement retailers that often have HVAC sections dedicated to heating and cooling components. They offer a variety of capacitors for different systems, and their large inventories ensure that you are likely to find what you need without having to wait for an order to be delivered.


An AC capacitor may be a small component, but it plays a vital role in keeping your cooling system running smoothly. It provides the power necessary for startup, ensures uninterrupted operation, and offers that extra juice during peak demand.

Whether you choose to buy online or locally, there are plenty of options available to find the perfect AC capacitor for your cooling needs. So next time you enjoy the blissful coolness of your air conditioner on a scorching summer day, remember to give thanks to the unsung hero inside – the AC capacitor.

AC Capacitors Online: Exploring Types, Ratings, and Specific Models

When it comes to purchasing AC capacitors online, it’s important to understand the different types, ratings, and specific models available. This knowledge will allow you to make an informed decision and ensure that you find the right capacitor for your cooling system.

In this section, we will delve into these aspects, providing detailed information to guide you in your online capacitor shopping journey.

Different Capacitor Types and Ratings

Before delving into specific capacitor models, let’s first explore the different types and ratings that you may come across while browsing online. The most common types of AC capacitors are dual run capacitors and single run capacitors.

Dual run capacitors are designed to provide power to two motors simultaneously, such as the condenser fan motor and the compressor. These capacitors have multiple capacitance ratings, typically expressed as a combination of two values separated by a “+” sign.

For example, you may encounter capacitors with ratings such as 35+5 MFD (microfarads) or 50+5 MFD. Single run capacitors, on the other hand, are used to power a single motor in your cooling system.

They typically have a single capacitance rating, such as 7.5 MFD or 40 MFD. These capacitors are commonly used for applications such as condenser fan motors.

When browsing online, you may come across reputable brands that offer a range of capacitor types and ratings. For example, TEMCo and MAXRUN are well-known manufacturers that provide high-quality capacitors for various cooling systems.

Their capacitors come in different capacitance ratings, voltages, and dimensions, allowing you to find the perfect fit for your specific system.

Specific Capacitor Models and Descriptions

Now, let’s take a closer look at some specific capacitor models and their descriptions, so you can better understand the available options when shopping online. 1.

TEMCo 7.5 uf/MFD: This capacitor is designed for single-phase motor applications, including air conditioners and refrigeration units. With a capacitance rating of 7.5 MFD and a voltage rating of 370 VAC, it is suitable for powering condenser fan motors.

2. TEMCo 40 uf/MFD: Featuring a capacitance rating of 40 MFD and a voltage rating of 440 VAC, this capacitor is commonly used in applications such as HVAC compressors and pool pump motors.

Its durable construction ensures reliable performance in demanding environments. 3.

MAXRUN 35+5 MFD: This dual run capacitor combines a capacitance rating of 35 MFD with a 5 MFD supplementary rating. With a voltage rating of 370 VAC, it is suitable for powering both the condenser fan motor and the compressor in your cooling system.

4. MAXRUN 40+5 MFD: Similar to the previous model, this capacitor is also a dual run capacitor with a capacitance rating of 40 MFD and a supplementary rating of 5 MFD.

Its voltage rating is 440 VAC, making it compatible with a wide range of cooling systems. 5.

TEMCo 45+5 uf/MFD: With a capacitance rating of 45 MFD and a supplementary rating of 5 MFD, this capacitor is a suitable choice for powering both the condenser fan motor and the compressor. It has a voltage rating of 370 VAC.

6. MAXRUN 50+5 MFD: Designed for dual run applications, this capacitor boasts a capacitance rating of 50 MFD and a supplementary rating of 5 MFD.

Its voltage rating of 440 VAC ensures compatibility with various cooling systems. 7.

MAXRUN 55+5 MFD: Similar to the previous model, this capacitor has a capacitance rating of 55 MFD and a supplementary rating of 5 MFD. Its voltage rating of 440 VAC makes it suitable for dual run applications.

8. MAXRUN 60+5 MFD: With a capacitance rating of 60 MFD and a supplementary rating of 5 MFD, this capacitor provides ample power for dual run applications.

Its voltage rating of 440 VAC ensures reliable performance. In addition to these models, there are other options available from reputable brands, such as PowerWell and BOJACK.

These capacitors come in various capacitance ratings and voltages, providing a wide range of options to suit different cooling systems.

AC Capacitors at Local Stores

While online shopping offers convenience and variety, you may prefer to purchase your AC capacitor from a local store. Fortunately, there are several options available when it comes to finding AC capacitors at local stores.

1. The Home Depot: A well-known home improvement retailer, The Home Depot often carries a range of AC capacitors in their HVAC section.

They provide online inventory information, allowing you to check the availability of specific capacitors at your local store. Their website also features product descriptions and customer reviews, helping you make an informed decision.

2. Lowe’s: Similar to The Home Depot, Lowe’s is another popular home improvement retailer that stocks AC capacitors.

You can browse their online inventory and check the availability at your local store. Detailed product descriptions and customer reviews are also available on their website.

3. Menards: Menards is a Midwest-based home improvement store that also offers AC capacitors in their HVAC section.

While their selection may vary by location, you can check their website for product availability and descriptions. Menards often provides competitive pricing on a wide range of products, including AC capacitors.

Considerations for Local Store Purchases

Before heading out to your local store, there are a few considerations to keep in mind when looking to purchase an AC capacitor. First, check the in-stock availability of the specific capacitor model you are interested in.

While larger stores like The Home Depot, Lowe’s, and Menards typically have a broad selection, it’s always prudent to make sure they have your desired capacitor in stock to avoid wasting a trip. If convenience is a priority for you, consider choosing a local store that offers online ordering with the option of local pickup.

This way, you can reserve the capacitor you need online, ensuring its availability before making the trip. Alternatively, if you prefer the ease of online shopping but still want to support a local business, consider checking if your local store has an online presence on platforms like Amazon.

Many local stores now have online storefronts on Amazon, providing you with the convenience of online shopping while supporting a local retailer.


Whether you choose to purchase an AC capacitor online or from a local store, understanding the different types, ratings, and specific models available is crucial. By exploring online options, such as dual run and single run capacitors from reputable manufacturers like TEMCo and MAXRUN, you can find the perfect capacitor for your cooling system.

Additionally, considering the availability and product descriptions offered by local stores like The Home Depot, Lowe’s, and Menards can help you make an informed decision. With this knowledge, you can confidently navigate the world of AC capacitors, ensuring the optimal performance of your cooling system.

AC Capacitor Buying Guide: From Types and Signs of Failure to Testing and Replacement

When it comes to buying an AC capacitor, there are several important factors to consider. Understanding the different types and subtypes, recognizing signs of a bad capacitor, knowing how to test and replace a capacitor, understanding the specifications and cost factors, and deciding between DIY and professional installation are all essential aspects that can help you make an informed decision.

In this AC capacitor buying guide, we will explore these topics in detail, providing you with the knowledge you need to ensure the smooth operation of your cooling system.

Capacitor Types and Subtypes

AC capacitors come in different types and subtypes, each serving a specific function in your cooling system. The two main types of AC capacitors are run capacitors and start capacitors.

Run capacitors, also known as motor-run capacitors, are common in air conditioning systems. They provide continuous power to the motor for efficient operation.

Run capacitors can be further classified into three subtypes: common (C), hermetic (HERM), and fan (F). The common (C) capacitor is used for general motor applications in the cooling system, such as the condenser fan motor.

The hermetic (HERM) capacitor is specifically designed for hermetically sealed compressors, while the fan (F) capacitor is used for the motor that powers the fan or blower in the system. On the other hand, start capacitors, or motor-start capacitors, provide an extra boost of power to get the motor started.

These capacitors are usually larger and have higher capacitance ratings than run capacitors. Start capacitors are not designed for continuous operation and are only used during the startup phase of the motor.

Signs of a Bad Capacitor

It’s important to be able to recognize the signs of a failing capacitor to address the issue promptly and prevent further damage to your cooling system. Some common signs of a bad capacitor include:


Aging: Capacitors have a limited lifespan and will degrade over time. If your capacitor is approaching the end of its lifespan (typically around 10-15 years), it may start to fail and exhibit performance issues.

2. Power Surges: Power surges can cause damage to capacitors, leading to their failure.

If your area experiences frequent power surges or if your cooling system has recently been exposed to a power surge, it’s advisable to check the capacitor for any signs of failure. 3.

Overheating: Excessive heat can also cause capacitors to fail. If your cooling system is not properly ventilated or if the capacitor is located in a spot where it gets too hot, it may degrade and eventually fail.

4. Outside AC Fan Not Working: A failing capacitor can cause the outside AC fan to stop working.

If you notice that the fan is not spinning, it’s worth checking the capacitor as a possible culprit. 5.

Inside Air Handler Spewing Hot Air: A malfunctioning capacitor can cause your air handler to blow hot air instead of cool air. If you experience this issue, it’s worth inspecting the capacitor for any signs of failure.

6. Capacitor Expansion or Bulging: A visual sign of a failing capacitor is expansion or bulging of the component.

Capacitors are typically cylindrical in shape, but if you notice any bulging, distortion, or leakage on the casing, it’s a clear indication that the capacitor needs to be replaced.

Capacitor Test and Replacement Process

If you suspect that your capacitor is failing, there are tests you can perform to confirm the issue. Here is a simplified process for testing a capacitor:


Turn off the power to your cooling system and discharge any residual electricity by using a wooden stick to bridge the terminals of the capacitor. 2.

Use a multimeter to test the capacitor’s capacitance. Set the multimeter to its capacitance function and connect the probes to the respective terminals of the capacitor.

A healthy capacitor should read within its specified capacitance range. 3.

If the capacitor fails the capacitance test or shows no capacitance reading at all, it is time to replace it. When replacing a capacitor, follow these steps:


Turn off the power to your cooling system and discharge any residual electricity. 2.

Note the orientation of the existing capacitor and disconnect the wires or terminals connected to it. 3.

Install the new capacitor in the correct orientation, matching the wire connections to the appropriate terminals. 4.

Double-check that all connections are secure and reapply power to test the new capacitor’s functionality.

Capacitor Specifications and Cost Factors

When purchasing an AC capacitor, there are several specifications and cost factors to consider. These include the shape of the capacitor, energy storage capacity (measured in microfarads or MFD), tolerance rating, voltage rating, and cost.

The shape of the capacitor is important to ensure compatibility with your cooling system. Different capacitors have different shapes, such as oval, round, or rectangular.

Measure the space available in your cooling system to determine the appropriate shape and size of the capacitor. The energy storage capacity or capacitance of the capacitor is a crucial specification.

It determines the amount of charge the capacitor can store and deliver to the motor. Refer to your cooling system’s specifications or consult a professional to determine the appropriate capacitance rating.

The tolerance rating indicates the allowable deviation from the stated capacitance rating. It is usually denoted as a percentage.

Lower tolerance ratings indicate higher accuracy. The voltage rating of the capacitor is another essential specification.

It must match or exceed the voltage requirements of your cooling system to ensure safe and efficient operation. Cost is also a significant factor when buying an AC capacitor.

Prices can vary depending on the brand, capacitance rating, voltage rating, and other factors. Compare prices from different retailers to ensure you get the best value for your money.

DIY vs. Professional Capacitor Replacement

Deciding whether to replace the capacitor yourself or hire a professional depends on your level of experience and comfort with HVAC systems.

Here are some considerations:

1. Tools: Capacitor replacement requires basic tools such as pliers, screwdrivers, and a multimeter for testing.

Assess your tool availability and your comfort level using them. 2.

Cost Range: DIY replacement can save you money on service fees. However, hiring a professional ensures that the replacement is done correctly and eliminates the risk of potential mistakes.

3. DIY Installation: If you have experience working with electrical components and feel confident in your abilities, you may opt for a DIY installation.

However, keep in mind that working with electrical components can be dangerous if not done correctly. 4.

Professional Installation: If you are unsure or uncomfortable working with electrical components, it is best to hire a professional. They have the expertise to safely replace the capacitor and ensure the proper functioning of your cooling system.

Additional Expenses: When considering a professional installation, keep in mind that there may be additional expenses involved, such as service fees or diagnostic charges. Factor in these costs when making your decision.

FAQs and Additional Information

Here are answers to some commonly asked questions about AC capacitors:

– Can I run my AC unit on a weak capacitor? Running your AC unit with a weak capacitor can lead to decreased performance and premature wear on the motor.

It’s advisable to replace a weak capacitor promptly. – How can I prevent capacitor failures?

Regular maintenance and cleaning of your cooling system can help prevent capacitor failures. Additionally, using surge protectors and keeping your electrical system well-maintained can protect capacitors from power surges and other electrical issues.

– Can I test a capacitor with a multimeter? Yes, a multimeter can be used to test capacitance.

Set the multimeter to the capacitance function and follow the testing process outlined earlier. – Can I use a start capacitor as a run capacitor?

Start capacitors are not designed for continuous operation and may overheat or fail if used as run capacitors. It’s essential to use the appropriate type of capacitor for the intended application.

– How long do capacitors last? Capacitor lifespan can vary depending on factors such as usage, operating conditions, and quality.

On average, capacitors can last around 10-15 years. Regular inspections and maintenance can help identify potential issues before they lead to failure.

– How do power surges affect capacitors? Power surges can cause damage to capacitors, leading to their failure.

Using surge protectors can help mitigate the risk of damage from power surges.


By familiarizing yourself with the different types and subtypes of capacitors, recognizing signs of a failing capacitor, understanding the testing and replacement process, considering capacitor specifications and cost factors, and deciding between DIY and professional installation, you can make an informed decision when buying an AC capacitor. Whether you choose to tackle the replacement yourself or enlist the help of a professional, having the knowledge to identify and address capacitor issues promptly is crucial for maintaining the optimal performance of your cooling system.

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