As summer heats up, the last thing anyone wants is an air conditioner malfunction. However, if your AC isn’t working correctly, a faulty capacitor could be the culprit. The capacitor is a vital component of an air conditioning system, but it’s easy to diagnose and fix if you know what to look for. In this article, we will explore the ins and outs of AC capacitors and provide a step-by-step guide on how to troubleshoot them to keep your AC unit running smoothly all season long.

1. Introduction: Understanding the Basics of an AC Capacitor

In order to troubleshoot an AC capacitor, you must first have a basic understanding of what it is and how it operates. AC capacitors are energy storage devices that help start and run motors in air conditioning systems. They store electrical charge in the form of an electrostatic field between two conducting plates separated by an insulator.

There are several types of AC capacitors commonly used in air conditioning systems, including run capacitors, start capacitors, and dual capacitors. Run capacitors are used to continuously provide voltage to motors while they’re running, while start capacitors provide the initial voltage needed to start a motor. Dual capacitors combine the functions of both run and start capacitors.

It’s important to understand the basics of an AC capacitor because it can help you diagnose problems with your air conditioning system. If you have a faulty capacitor, it can prevent your AC system from starting or running efficiently. In the next section, we’ll discuss some signs of a faulty AC capacitor and why it matters.

Types of AC Capacitors

There are several types of AC capacitors commonly used in air conditioning systems, including:

  • Run Capacitors
  • Start Capacitors
  • Dual Capacitors

How AC Capacitors Work

AC capacitors store electrical charge in the form of an electrostatic field between two conducting plates separated by an insulator. They help start and run motors in air conditioning systems by providing voltage to the motors. Run capacitors continuously provide voltage, while start capacitors provide the initial voltage needed to start a motor. Dual capacitors combine the functions of both run and start capacitors.

2. Signs of a Faulty AC Capacitor and Why it Matters

Before you can start troubleshooting your AC capacitor, it’s crucial to know the signs of a faulty capacitor. Here are three common signs that your AC capacitor may be faulty:

1. AC Unit Not Turning On

If your AC unit fails to turn on, it could be due to a faulty capacitor. The capacitor is responsible for supplying the initial jolt of electricity that starts the motor. If the capacitor is unable to supply enough power to start the motor, your AC unit will not turn on.

2. Diminished Cooling Power

If you notice that your AC unit isn’t cooling your home as effectively as it once did, it’s possible that the capacitor is failing. A capacitor that isn’t supplying enough power to the motor can cause the unit to struggle to cool your home, resulting in decreased cooling power.

3. Strange Noises and Smells

If you notice unusual noises or smells coming from your AC unit, it could be a sign of a failing capacitor. A capacitor that isn’t functioning correctly can cause the motor to overheat, resulting in strange noises and potentially even a burning smell.

While a faulty capacitor may not seem like a significant issue, it can have a significant impact on your AC unit’s overall efficiency and lifespan. A capacitor that isn’t operating correctly can place undue strain on your AC unit, leading to more significant and potentially more costly repairs down the line. Catching and fixing capacitor issues early can save you a lot of time, money, and frustration in the long run.

3. Step by Step Guide to Troubleshoot an AC Capacitor

To troubleshoot an AC capacitor, you need a few basic tools like a multimeter, screwdriver, and electrical tape. Here’s a step-by-step guide to help you get started:

Step 1: Turn off the AC Unit

Before checking the AC capacitor, switch off the power supply from the electrical panel or breaker box to the AC unit.

Step 2: Locate the Capacitor

The AC capacitor is usually a cylindrical-shaped or oval-shaped container connected to the fan motor and compressor. It’s placed on the outside part of the AC unit.

Step 3: Identify the Type of Capacitor

An AC capacitor can be of two types – run capacitor or start capacitor. The run capacitor operates throughout the AC unit’s operation, whereas the start capacitor provides a boost to the compressor and fan motors during startup.

Step 4: Test the Capacitor with a Multimeter

Set your multimeter to ohms. To test the capacitor, you need to measure the resistance in the capacitor with a multimeter. Connect the leads of the multimeter with the terminals of the capacitor. The reading on the multimeter should quickly climb and then fall back to infinite resistance.

Step 5: Check for Physical Damage or Bulging

Sometimes, physical damage or bulging may occur in the capacitor due to overheating or aging. Look for any signs of bulges, cracks, or leaks on the surface. If you find any physical damage, you’ll need to replace the capacitor.

Step 6: Install a New Capacitor

If you find that the capacitor is faulty, you must replace it with a new one of the same size and specifications. Do not operate the AC unit with a faulty capacitor.

By following these simple steps, you’ll be able to troubleshoot a faulty AC capacitor with ease. However, if you’re unsure about the process, it’s advisable to engage a professional HVAC technician for the job.

4. Common Problems and Solutions When Troubleshooting AC Capacitors

When troubleshooting an AC capacitor, there are several common problems that you might encounter. Here are some of the potential issues you might come across and some solutions to fix them:

1. Bulging or Leaking Capacitor

One of the most common issues you might encounter when troubleshooting an AC capacitor is a bulging or leaking capacitor. This often happens when the capacitor overheats or has been damaged by power surges. If you notice that your capacitor looks swollen or is leaking oil, it’s important to replace it as soon as possible. Continuing to use a damaged capacitor can cause serious damage to your AC system.

2. Weak Capacitor

Another problem that you might come across is a weak capacitor. This can cause your AC unit to struggle to start up and may result in poor cooling performance. To troubleshoot this problem, you can use a multimeter to test the capacitor’s voltage. If the voltage is below the manufacturer’s recommended range, you’ll need to replace the capacitor.

3. Short-Circuited Capacitor

If your AC capacitor is short-circuited, it can cause your AC unit to stop working altogether. This can happen if there’s a problem with the wiring or if the capacitor has been damaged in some way. To fix this issue, you’ll need to inspect the wiring and test the capacitor’s resistance. If the resistance is too low or there are other signs of damage, you’ll need to replace the capacitor.

In conclusion, troubleshooting an AC capacitor requires careful attention to detail and a good understanding of how these components work. By familiarizing yourself with common problems and solutions, you can quickly diagnose and repair any issues that may arise with your AC system. Remember to always prioritize safety and seek professional help if you’re unsure about any aspect of the troubleshooting process.

5. Professional Help: When to Call an HVAC Technician for AC Capacitor Issues

Knowing when to call an HVAC technician can save you time and money while ensuring that your AC capacitor problem is solved efficiently. Here are some situations when it’s best to leave the troubleshooting and repair work to the professionals.

1. Lack of Experience in Electrical Work

If you’re not confident in handling electrical work and don’t have the necessary experience in troubleshooting and repairing electrical systems, it’s best to leave the job to an HVAC technician. Working with electrical systems without proper knowledge and training can be dangerous and lead to further damage to your AC system or even pose a risk to your safety.

2. Frequent AC Capacitor Failures

If your AC capacitor is failing frequently, it could be a sign of more significant issues with your AC system. An HVAC technician can diagnose the root cause of your AC capacitor problem, inspect your AC system, and provide a long-term solution to avoid frequent capacitor failures.

3. Unusual or Complicated AC Capacitor Problems

Some AC capacitor problems can be simple to diagnose and fix, while others may require expertise and specialized equipment to solve. Unusual symptoms such as melted capacitors, buzzing sounds, or burnt wires should be addressed by an HVAC technician who can accurately diagnose the problem and perform the necessary repairs.

Professional help can not only save your time and money but also ensure that your AC system is working efficiently without any safety risks.

6. Preventive Maintenance Tips to Avoid AC Capacitor Troubleshooting

To avoid any downtime or costly repairs, preventive maintenance of AC capacitors is crucial. Here are some tips to keep your AC capacitor in top condition and avoid troubleshooting:

Clean and Inspect Regularly

Preventive maintenance should be done regularly to ensure that the AC capacitor is functioning correctly. The first preventive maintenance step is to clean the component regularly. Dirt, dust, and debris may interfere with the operation of the capacitor and cause damage. Clean the area around the component regularly to ensure that it doesn’t get clogged with debris.

Check the Connections

Loose or corroded connections between the capacitor and motor or AC unit can cause power supply issues, resulting in failure of the capacitor. Check the connections periodically, tighten loose connections and replace corroded and damaged wires.

Replace Old and Worn Out Capacitors

You should replace the capacitor after every three to five years, depending on usage. Old and worn-out capacitors can lead to voltage fluctuation and can damage other components of the AC unit.

Maintain Correct Voltage Range

Most AC capacitors have voltage ranges that they function in. Voltages outside the recommended range can lead to failure and damage. Ensure that the voltage in your power supply falls within the recommended range by checking the voltage readings with a multimeter.

Turn off the AC unit Before Maintenance

Before carrying out any maintenance on the AC capacitor or any other component of the unit, turn off the AC unit. This will protect you from accidental shocks and possible damage to components.

Preventive maintenance helps you avoid costly repairs and ensures that your AC unit is functioning optimally. By following these simple tips, you can avoid any issues with your AC capacitor.

7. Conclusion: Importance of Proper AC Capacitor Maintenance and Troubleshooting

AC capacitors are a vital component of any HVAC system, and a faulty capacitor can lead to serious damage to the system as well as the risk of injury to the occupants. As such, it is essential to understand the basics of AC capacitors and the importance of troubleshooting and maintenance to keep your HVAC system running smoothly.

Proper Maintenance and Troubleshooting Can Save You Time and Money

Proper maintenance and troubleshooting of your AC capacitor can help you avoid costly repairs and replacements down the line. By regularly inspecting and testing your capacitor, you can catch issues early and address them before they become bigger problems. This can save you time and money in the long run.

Additionally, regular maintenance can help extend the lifespan of your HVAC system, ensuring that it runs efficiently and effectively for years to come. By taking the time to troubleshoot and maintain your AC capacitor, you can ensure that your HVAC system continues to provide reliable cooling and heating to your home or business.

Work with a Professional for Peace of Mind

While DIY troubleshooting and maintenance is possible for those with some experience and knowledge of HVAC systems, it is always best to work with a professional for peace of mind. An experienced HVAC technician can help you with routine maintenance and troubleshooting, as well as provide guidance on when it is time to replace a faulty capacitor.

By working with a professional, you can rest easy knowing that your HVAC system is in good hands. Whether you need a simple capacitor replacement or a full system repair, a skilled technician can ensure that your HVAC system runs safely and efficiently.

In conclusion, proper maintenance and troubleshooting of your AC capacitor is essential to ensure the continued operation of your HVAC system. By understanding the basics of AC capacitors and working with a professional when needed, you can keep your system running smoothly and avoid costly repairs and replacements down the line.

People Also Ask:

1. What are the signs of a bad AC capacitor?

A few signs that indicate a bad AC capacitor include the AC compressor not turning on, a humming noise from the AC unit, inconsistent or weak airflow, and inconsistent cooling.

2. How do you test an AC capacitor?

To test an AC capacitor, you need a multimeter that has a capacitance setting. Discharge the capacitor, connect the multimeter leads to the appropriate terminals, and read the capacitance value. Compare it with the manufacturer’s specifications to check if it’s working correctly.

3. Can you replace an AC capacitor yourself?

Yes, you can replace an AC capacitor yourself. However, it’s important to ensure that you have the right capacitor with the correct specifications and voltage rating. Additionally, it’s crucial to turn off the power supply and discharge the capacitor before replacing it.

4. What happens when AC capacitor goes bad?

When an AC capacitor goes bad, the AC system may not function correctly. The unit may not start, or it might shut off after a short while. Additionally, a bad capacitor can cause the motor to overheat, leading to burnouts and failure.

5. How long does an AC capacitor last?

An AC capacitor can last anywhere from 5 to 20 years, depending on the usage and quality of the capacitor. However, if you notice any signs of a bad capacitor, it’s crucial to replace it immediately to avoid any further damage to your AC system.


Troubleshooting an AC capacitor can be challenging, but it’s essential for maintaining the efficiency and longevity of your AC system. It’s crucial to keep an eye out for any signs of a bad capacitor and replace it with the right specifications and proper voltage rating. Additionally, it’s essential to discharge the capacitor and turn off the power supply before attempting any repairs or replacements. Regular maintenance and inspections can help prevent any significant issues with your AC system.