How to Test an Air Conditioner Capacitor: Steps to Test AC Capacitor

Air conditioners keep you cool and comfortable in the hot summer months. However, if your AC unit isn’t functioning correctly, one common culprit might be a faulty capacitor. This article will show you how to test an air conditioner capacitor. This will help you find and fix any problems.

How to Test an Air Conditioner Capacitor
How to Test an Air Conditioner Capacitor

Understanding the Air Conditioner Capacitor

Your air conditioner comprises different parts that work together to keep your home cool. One important part of your AC unit is the air conditioner capacitor. It helps your AC work well. In this section, we will delve into the world of the air conditioner capacitor, demystifying its function and significance.

What is an Air Conditioner Capacitor?

An air conditioner capacitor is a small electrical device that stores and releases electrical energy. The unit stores power temporarily. It gives the jolt to start your AC’s compressor and fan motor. Without a functioning capacitor, your air conditioner couldn’t kickstart its cooling process.

Types of Air Conditioner Capacitors

There are two primary types of air conditioner capacitors, each serving a specific function in the AC system:

1. Start Capacitors

Start capacitors give the first jolt of electricity to kickstart the compressor motor. They’re important in one-phase air conditioners for a smooth and efficient start. Start capacitors are made to give a big electrical push to start the motor quickly.

2. Run Capacitors

Run capacitors, on the other hand, play a different role. They are responsible for maintaining a consistent flow of electricity and keeping the compressor and the condenser fan running throughout the cooling cycle. Run capacitors have lower capacitance values than start capacitors and are designed for continuous operation.

The Capacitor’s Role in the AC System

The air conditioner capacitor works like a heartbeat in your body. It stores electricity, just like your heart stores and pumps blood. When you turn on your air conditioner, it needs a big burst of electricity to start the compressor motor and the condenser fan. The capacitor gives out this stored electricity to make these parts move.

The compressor is super important in your AC. It moves refrigerant, which takes the heat from your home’s air. The condenser fan helps cool down the hot refrigerant. If the capacitor doesn’t work, the compressor and fan can’t start, and your air conditioner won’t work.

Signs of a Failing AC Capacitor

The capacitor plays a pivotal role in the functionality of your air conditioning system. It stores and releases electrical energy, enabling your air conditioning unit to start and run smoothly. A failing capacitor can lead to various issues in your cooling system. Here are the telltale signs that your AC capacitor might be on the verge of failing:

1. Weak Cooling Performance

A common sign that your AC capacitor might fail is when your air conditioner doesn’t cool well. Even if you set it to the coldest mode, if it can’t keep your place cool, it might be because the capacitor is weak or failing. The capacitor’s main job is to give a strong burst of electricity to start the compressor. If it can’t do this well, your AC won’t cool your space correctly.

2. Frequent AC Shutdowns

If your air conditioner keeps turning off for no apparent reason, it could be because of a problem with the capacitor. The capacitor’s job is to ensure the electricity flows smoothly to the compressor and the fan. The electricity becomes unstable when the capacitor doesn’t work right, so your AC might shut down unexpectedly.

3. Prolonged Cooling Times

If your air conditioner takes a really long time to get as cool as you want, there’s a problem. A bad capacitor can make it take longer to cool down, which means your AC uses more energy and you have to wait longer for comfort.

4. Unusual AC Noises

Listen carefully to your air conditioner. Unusual sounds like clicking, buzzing, or humming can indicate capacitor problems. When the capacitor can’t provide the necessary electrical boost to start the compressor, it can lead to mechanical strain and odd noises.

5. AC Compressor Doesn’t Start

If your AC compressor refuses to start or experiences delays, it could be due to a failing capacitor. The capacitor provides the initial kick-start to the compressor motor, and when it can’t do this effectively, the compressor may fail to initiate.

6. High Energy Bills

A failing capacitor can lead to an inefficient AC unit. When your air conditioner has to work harder to cool your space due to a weak capacitor, it increases energy consumption and energy bills.

7. Burning Odor

A bad capacitor can get very hot and make a burning smell sometimes. If you smell something strange like that from your AC, turn it off right away and get help from a pro.

Knowing when your AC capacitor is failing is important to keep your AC working well. If you see these signs, it’s smart to call a technician to fix it quickly. Changing the capacitor on time can prevent more extensive, more expensive AC repairs later.

How to Test an Air Conditioner Capacitor: Step By Step Guide

Now that you know how important the air conditioner capacitor is, let’s go through the steps to test it. To get started, make sure you have these essential tools:

  1. Screwdriver
  2. Multimeter

Follow these steps to conduct a successful test and ensure your air conditioner capacitor is in good working condition:

Step 1: Safety First

Prioritizing safety above everything else is crucial when handling electrical components. Start by turning off the power to your air conditioner. This can typically be done at the electrical panel by switching off the corresponding circuit or disconnecting the unit from the power source. This step is essential to prevent electrical shocks or accidents during testing.

Step 2: Access the Capacitor

You’ll need to open the access panel on your air conditioner to access the capacitor. The capacitor is usually located near the fan and compressor. When dealing with electrical components, exercise caution and be mindful of safety. Ensure that the power remains off during this step to avoid any accidents.

Step 3: Discharge the Capacitor

It must be discharged thoroughly before safely handling the capacitor to prevent residual electrical energy. Use an insulated screwdriver to accomplish this. Touch the screwdriver’s metal end to both capacitors’ terminals simultaneously. This creates a short circuit and safely dissipates any stored electrical charge. Be cautious when performing this step, as avoiding electrical shocks is essential.

Step 4: Test the Capacitor

Set your multimeter to the capacitance setting. Verify that the multimeter is accurately calibrated and operating. Now, carefully touch the multimeter’s probes to the terminals of the capacitor. The multimeter should provide a reading close to the capacitor’s rated capacitance value. This value is usually specified on the capacitor or your air conditioner’s manual. If the multimeter reading significantly deviates from the rated capacitance value, it indicates that the capacitor is faulty and may need to be replaced.

Step 5: Testing Start and Run Capacitors

It’s essential to remember that start and run capacitors have different capacitance values. Ensure you test the appropriate capacitor based on your observations. Start capacitors usually have significant capacitance and help kickstart the compressor motor. Run capacitors have smaller capacitance, keeping the compressor and fan going during cooling.

By doing these steps, you can check your AC’s capacitor and see if it’s good. Regular testing ensures it works well and keeps your unit running reliably and efficiently.

The Importance of Testing the AC Capacitor

In the world of air conditioning, one small yet crucial component often goes unnoticed—the AC capacitor. This unassuming device stores and releases electrical energy, kickstarting your AC’s vital components. Testing your AC capacitor is paramount for these key reasons:

  • Reliable Operation: A functioning capacitor ensures your AC starts and runs smoothly. Regular testing guarantees you won’t be left without cool air on scorching days.
  • Preventing Breakdowns: Testing detects potential issues before they lead to costly and unexpected AC breakdowns. Don’t wait for discomfort or emergency repairs.
  • Energy Efficiency: A well-maintained capacitor leads to energy savings. Avoid the extra expense of an overworked AC by keeping your capacitor in top shape.
  • Prolonged Lifespan: Testing can extend your capacitor’s life, saving you from the hassle and cost of replacement.
  • Cost-Efficiency: Addressing capacitor issues early on prevents more extensive, expensive AC problems.
  • Consistent Cooling: Enjoy reliable, efficient cooling for your comfort and well-being.

Remember, safety is essential when you’re testing your AC capacitor. Turn off the power and follow proper discharge procedures to avoid accidents. When in doubt, seek professional help for peace of mind and accurate testing.

Replacing a Bad Capacitor

If you’ve tested your air conditioner’s capacitor and found that it’s no longer functioning correctly, it’s essential to replace the capacitor promptly to ensure your cooling system operates efficiently. Here’s a step-by-step guide on how to replace a bad AC capacitor:

Tools and Materials You’ll Need:

  • New capacitor: Ensure that the AC capacitor replacement capacitor matches the specifications outlined by the manufacturer, including capacitance value and voltage rating.
  • Screwdriver
  • Needle-nose pliers
  • Insulated gloves
  • Safety goggles
  • Work gloves
  • Electrical tape
  • Digital Multimeter
  • Marker
  • Zip ties or cable ties
  • Replacement wires (if damaged)

Safety First:

Turn off the power to your AC to avoid electrical shocks.

Discharge the Old Capacitor:

Safely dissipate any stored electrical energy using an insulated screwdriver.

Identify Wires:

Label and note how wires are connected for accurate reattachment.

Remove the Old Capacitor:

Disconnect the wires from the capacitor, unscrew the old capacitor, and remove it from the AC.

Install the New Capacitor:

Securely attach wires to the new capacitor following your labels.

Secure the New Capacitor:

Reattach the new capacitor in its original location.

Insulate and Organize:

Use electrical tape and zip ties to protect wires and maintain a neat setup.

Restore Power:

Reconnect the power to the AC unit.

Test the System:

Please turn on your air conditioner and ensure it runs smoothly, with the compressor and fan working as expected.

Regular Maintenance:

Schedule regular AC maintenance, including capacitor inspections, to prevent future issues.

If you’re uncomfortable with any step, consider HVAC professional assistance for a safe and accurate capacitor replacement.

Common AC’s Capacitor Issues

Air conditioner capacitors are essential to your cooling system, providing the electrical energy required to start the compressor and condenser fan. While they are built to be durable, capacitors can experience problems over time. Here are some common AC capacitor issues that you may encounter:

Capacitor Aging

Capacitors, like all electrical components, have a finite lifespan. Their ability to store and release electrical energy can diminish as they age. This can result in a weakened electrical boost, leading to startup problems for the compressor and condenser fan.

Capacitor Damage

Physical damage to the capacitor can occur due to various factors, including exposure to the elements, extreme temperatures, or accidental impact. Cracks or other forms of damage can compromise the capacitor’s functionality.

Electrical Overload

Electrical surges or frequent power fluctuations can put stress on the capacitor. Over time, this can lead to reduced performance or even failure. Surge protectors can be used to lessen this problem.


Dust, dirt, and debris can accumulate on the capacitor’s terminals. This can disrupt the electrical connection and affect its performance. Regular maintenance, including cleaning, can prevent this problem.

Incorrect Capacitor

Using the wrong type of capacitor, one with an incorrect capacitance value or voltage rating can lead to problems. The capacitor must match the specifications outlined by the manufacturer to ensure proper functioning.

Weak or Failed Start Capacitor

Start the capacitors, which provide the initial electrical boost to the compressor, can become weak or fail. This can result in the compressor struggling to start or failing to start at all.

Weak or Failed Run Capacitor

Run the capacitors, responsible for maintaining a steady flow of electricity to the compressor and condenser fan, can also weaken or fail. This may lead to issues such as inefficient cooling and prolonged cooling times.

Contactor Issues

The contractor, a part of the AC unit’s electrical system can become faulty and fail to send the necessary electrical signal to the capacitor. The capacitor won’t discharge its stored energy correctly when it doesn’t receive the signal.


Corrosion on the capacitor terminals or wiring connections can disrupt the electrical flow. This often occurs in outdoor units exposed to the elements. Regular inspections and maintenance can prevent corrosion-related issues.

Heat-Related Problems

Capacitors are sensitive to temperature extremes. High temperatures can cause them to overheat and fail, while extreme cold air can reduce efficiency. It’s essential to protect the capacitor from such conditions.

Knowing these capacitor problems can help you resolve issues with your cooling system. If you see these problems, get a technician to check and fix them so your AC works well. Testing and keeping the capacitor in good shape can prevent these problems.


Testing an air conditioner capacitor is a valuable skill that can help you maintain a cool and comfortable indoor environment. Following the steps and safety precautions outlined in this guide, you can diagnose capacitor issues and take the necessary steps to resolve them.


Can I test my air conditioner capacitor without any prior experience?

Testing a capacitor requires some basic electrical knowledge. If you’re not confident, it’s best to seek professional assistance.

How often should I test my capacitor?

Testing your capacitor whenever you face cooling issues or hear strange noises from your Air Conditioner unit is good practice.

Can a faulty capacitor damage other parts of my air conditioner?

Yes, a faulty capacitor can lead to additional wear and tear on other components, so addressing the issue promptly is crucial.

Are there any risks involved in testing the capacitor myself?

Electrical risks are involved, so always turn off the power and follow safety precautions. If unsure, consult a professional.

What if my capacitor tests within the specified range, but I’m still experiencing AC problems?

If your capacitor tests fine, there may be other issues with your AC. It’s advisable to consult a technician for a thorough diagnosis.

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