How To Test An AC Capacitor With A Multimeter? [Updated Guide]

Multimeters should be used to test AC capacitors to ensure the safety of your electrical system. Follow the instructions in this guide on how to test an AC capacitor with a multimeter to make sure they’re working properly. The capacitor also helps reduce the amount of electricity the air conditioner consumes, making it more energy efficient. To keep your air conditioner running smoothly and efficiently, you should replace the capacitor every three years. If your capacitor is not functioning correctly, your air conditioner may be using more energy than it needs to, resulting in higher electricity bills.

What causes a capacitor to fail?


Overvoltage causes a capacitor to experience excessive electrical stress beyond its rated limit. The strain can rupture the dielectric material, resulting in a breakdown. It is common for capacitors to fail due to overvoltage situations caused by power surges, incorrect circuit connections, or sudden voltage spikes.


What causes a capacitor to fail

It is possible for capacitors exposed to high temperatures to age and deteriorate faster. Heat exposure causes the electrolyte to evaporate, reducing the capacitor’s effectiveness and eventually resulting in failure. Poor ventilation, proximity to heat sources, and excessive current flow are common causes of overheating.

Physical Damage:

Capacitors can be damaged by external forces or mechanical stress. Handling, installation, or environmental factors may cause physical damage. Casings with cracks or bends compromise the capacitor’s integrity, allowing contaminants to enter or altering its electrical properties, eventually resulting in failure.


The lifespan of a capacitor is finite. Dielectric materials degrade with time, reducing the capacitor’s ability to store and release charge effectively. In addition to use, temperature variations, and the quality of materials used in manufacturing, aging is a natural process. Over time, the capacitor becomes more prone to failure as it ages.

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How To Test An AC Capacitor With A Multimeter| 4 Easy Steps

To prevent potential AC system failures, it is essential to test an AC capacitor with a multimeter. The capacitor stores electrical energy, enabling motors to start and operate consistently. A multimeter is helpful in determining whether a capacitor is working properly or needs to be replaced.

Step#1 Safety Precautions:

Be sure to turn off the power to the AC unit before testing to prevent electrical shocks or damage. By bridging the capacitor’s terminals with an insulated screwdriver, you can avoid any stored electrical charge that might be harmful.

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Step#2 Selecting the Multimeter Settings:

How To Test An AC Capacitor With A Multimeter

Select the capacitance or ohms setting on the multimeter. In case the multimeter has a manual range selection, choose the appropriate range for capacitance. The ohms mode can also be used in some cases, selecting a range higher than the expected capacitance.

Step#3 Discharging the Capacitor:

how to discharge capacitor

To short the capacitor’s terminals, use an insulated screwdriver. The screwdriver should be held across both terminals for a few seconds in order to dissipate any residual charge. During testing, this step minimizes the risk of electric shock.

Step#4 Testing Capacitance:

How To Test An AC Capacitor With A Multimeter

The leads of the multimeter must be placed on the terminals of the capacitors. The capacitance mode of the multimeter must be set for capacitance testing. For polarized capacitors, connect black probe to positive terminal and red probe to negative terminal. Check this reading against the capacitor’s rated capacitance. A significant deviation indicates that the capacitor needs to be replaced. Now you know how to test an AC capacitor with a multimeter but do you think why is important to test a capacitor? Take a short look at the next section.

Why is it essential to test an air conditioner capacitor?

It is important to test an air conditioner capacitor to ensure that it operates efficiently. In the event that the capacitor fails, the AC will not start or may struggle, affecting cooling. In the event of a sudden breakdown, regular testing can prevent costly repairs or replacements. Capacitance levels can be checked to detect weakening or faulty capacitors, preventing damage to other AC components. In hot weather, timely AC testing ensures optimal performance, extends the AC’s life, and keeps you comfortable.

What is the purpose of a capacitor on an air conditioner?

The air conditioner capacitor helps regulate the flow of electricity through the unit. It helps to keep the AC running smooth and prevents it from shorting out. The capacitor stores energy, which is then released in short bursts when needed to power the compressor and other components of the air conditioner.

It helps to keep the AC running efficiently and reduces electricity consumption. Capacitors should replace every three years to keep your air conditioning system working properly.If you wanted to learn Fluke vs klein then,you can click here.

Can an air conditioner work without a capacitor?

No. An air conditioner cannot work without a capacitor. The capacitor is used to start the compressor; without it, the air conditioner will not work. The capacitor also helps to regulate the flow of electricity and keeps the air conditioner running smoothly. It should test regularly and replaced when necessary to keep your air conditioner working properly. I made the list of best budget multimeters you can check out.


I hope after reading this article, you must able to answer how to test an AC capacitor with a multimeter. Testing an air conditioner’s capacitor is essential for optimal performance and energy efficiency. The capacitor helps start the compressor in the air conditioner and helps to regulate the flow of electricity, keeping your AC running smoothly.

It should test regularly and replaced every three years to prevent potential problems and keep your AC working properly. Taking the time to test your capacitor will save you money in the long run by reducing energy consumption and avoiding costly repairs.


What happens if the capacitor fails in AC?

The capacitor is an essential component in an AC system because it helps to regulate the flow of electricity. If the capacitor fails, it can cause the system to become overloaded and trip the breaker. In some cases, it can also damage other components in the system.

How long does a capacitor last in an air conditioner?

A capacitor in an air conditioner should last anywhere from 5 to 10 years, but it’s essential to keep an eye on it and replace it when necessary. Signs that a capacitor is going bad include a clicking noise when the AC is turns on or a decrease in the amount of cold air produced.

How to an air conditioner capacity with a Voltmeter?

There’s no definitive answer to this question since the capacity of an air conditioner can vary depending on the size and type of unit and the climate conditions in which it’s being used. That said, here are a few general tips that might help you get a ballpark estimate of an air conditioner’s capacity:

  • First, you’ll need to determine how many volts your air conditioner runs on. This information should list in the owner’s manual or the unit itself. Once you have this number, divide it by 12 to get the amps rating.
  • Next, you’ll need to measure the amperage draw of your AC unit. It can be done with a simple voltmeter. With the AC unit running, set the voltmeter to “amps” and measure the amount of current drawn. It will give you a rough idea of its capacity.
  • Finally, consider any additional factors that might affect an air conditioner’s capacity, such as climate conditions and the size of the unit itself. It will help you get a more accurate estimate.