What Is Air Conditioner Capacitor?

Aircon Capacitor

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Air conditioner capacitor helps the air conditioner to start up. Don’t underestimate the capacitor!

If capacitor is broken, the entire air conditioner will stop cooling. This is also the most common fault for air conditioner.

Today we will talk about knowledge of capacitors.

What Is Capacitor

Definition: Any combination of two conductors separated by an insulator is called capacitor, also called capacitance.


Capacitor Parameter

Text symbol of the capacitor is: C

Important indicators: Electric capacity (uF), withstand voltage (380V/220V)

For example 35 uF, 220V means: the capacitance is 35 uF, the withstand voltage is 220V

The total capacitance of the parallel capacitors is equal to the sum of the capacitances of the individual capacitors.

That is: C=C1+C2+C3

Capacitor Classification

According to the different dielectrics and materials, capacitors can be divided into: ceramic capacitors, mica capacitors, mica capacitors, and paper capacitors.

According to the polarity, divided into: non-polar capacitors and electrolytic capacitors with positive and negative electrodes.

Air-conditioning capacitors generally use fixed paper capacitors.

Importance of Air Conditioning Capacitor

Air-conditioning capacitor is a device that starts the motor (compressor motor or fan motor). If the motor doesn’t rotate after the power is on, that means the capacitor is broken.

Once the capacitor is damaged, meanwhile the motor doesn’t rotate, then the fan won’t work, and eventually, the air conditioner won’t work properly.

Therefore, capacitor is a very important component of the air conditioner.


Air-conditioner Capacitor

The Harm of Wrong Starting Capacitor

If the capacitor capacity is too large, will easily cause the motor to increase the working current during operation, the motor is easy to burn; If the capacity is too small, the starting torque will become smaller, and the motor has no power, and speed drops, finally the motor is difficult to start or completely can’t start.

Therefore, a reasonable choice of capacitors is necessary.

How to Detect The Capacitor Quality?

1). Connect the 220V AC power directly

You can connect one pole first, and touch the other capacitor pin with the other power cord.
If the spark generated when touching is very small, you can be sure that the capacitor is chargeable, which means the capacitor is not broken.

2). Pointer multimeter testing

Generally use the R × 1K row, and connect the test leads to the two poles of the capacitor respectively.

The multimeter pointer will swing and then slowly return to or close to the zero position. It shows that such a capacitor is good. The larger the capacitor capacity, the longer the charging time, and the slower the pointer swings in the “00” direction.

If the pointer doesn’t move or the swing range is small after connecting it, certainly the capacitor is broken.

Pointer multimeter with “1K”

3). Digital multimeter testing

Check with a digital multimeter, set the digital multimeter to the appropriate resistance range, and the red and black test leads respectively touch the 2 poles of the capacitor under test.

Then the displayed value will gradually increase from “0” until the symbol “1”. If always display “0”, it means that the capacitor is short-circuited. If always display “1”, it may be an open circuit between the internal electrodes of the capacitor, or it may be that the selected resistance file is not suitable.

Digital multimeter testing

Digital Multimeter

4). Use a multimeter to set the function switch to 20uF or 200uF

The test leads are placed in the middle of 2 holes. The test leads are used to measure the two poles of the capacitance respectively, and then its capacity will be displayed. If it is a used capacitor, it must be discharged before measurement.

The principle of selecting the resistance range: When the capacitor is large, should use a low-resistance range; when the capacitor is small, should select a high-resistance range.

Selection of resistance when measuring capacitor

After the capacitor is broken down (can’t repair), you have to replace it with a new capacitor of the same model. In order to facilitate the selection during repair, the following table lists the matching capacity of the capacitor and the output power of the compressor motor, enjoy.

Capacitor Capacity

Broken Air Conditioner Capacitor Features

1. Bulge

Bulge Capacitor

2. Smoke

3. Can’t operate

4. Indoor screen panel can’t display

5. The power supply can’t be discharged

6. Can’t heat

From the following video you can diagnose or replace the air conditioner capacitor, enjoy↓


Air conditioner has two capacitors: the larger one is compressor capacitor, and the smaller one is the capacitor of the outdoor unit.

1. The large broken capacitor will jitter and bring noise

You will find that there is a relatively loud noise when the compressor switches on, and the air conditioner outdoor unit is constantly shaking. If putting your hand on the AC outdoor unit,  your hands are also shaking.

At the same time, the noise of the air conditioner is also very loud, and the compressor will stop running soon.

2. The small capacitor is the capacitor of the outdoor unit

This capacitor feature: the compressor can work normally at first, but after a few times, both the indoor unit and the outdoor unit will stop running.

Maintenance: Broken capacitor has a great influence on the air conditioner. Therefore, we don’t recommend you repair it yourself, mustn’t remove the parts inside the air conditioner privately. This will affect the service life of the air conditioner.

You should ask your capacitor supplier, or contact a professional service company for help.

Inside of the capacitor

What’s inside a capacitor

How to Buy Air Conditioning Capacitor?

1. When buying an Air Conditioning capacitor, first observe the appearance of the capacitor to avoid any deformation or cracking at the surface. In this case, never buy it, because that must be a quality problem.

In addition, pay attention to whether it is the same model as the broken one. Doesn’t use the capacitor model randomly, as that will damage the air conditioner.

2. When you buy a capacitor, you also need to look at its capacity.

Generally, the capacity of a capacitor will slowly decay as the use time is longer or the environment changes. If the capacity of the capacitor decays to 20% of the total, it will be difficult to start the air conditioner.

Therefore, we should choose a larger capacitor within the tolerance range of the air conditioner to ensure that the air conditioner can use for a longer time.

3. When purchasing capacitors for air conditioner, try to buy some well-known brand products. After all, the quality of big brands is more secure and better for the use of air conditioner.

 Air Conditioner Capacitor

4. Capacitors are very important for air conditioners, so you must carefully read every detail in the manual when buying, especially the packaging of capacitors, so as to see if the packaging is damaged or squeezed, in order to avoid buying damaged products.


The air conditioner capacitor seems to be a small part, but it is of great significance to the normal operation of the air conditioner.

If there is a problem with the operation of an air conditioner, you can check whether the problem is the capacitor (based on the above knowledge). If yes, then you should replace the broken part immediately, to avoid affecting the normal operation of the air conditioner, especially can’t damage the compressor, because the compressor is the most expensive part of the whole air conditioning system.

Knowing some air conditioning maintenance knowledge will also be very helpful for you.

Any comments?

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About Author

Vic Cheung
Vic Cheung

Hi, I'm Vic! Start working in HVACR field since 2008, our main products included: air conditioning, cold room refrigeration system, water chiller, ice machine, commercial dehydrator, dehumidifier, heat pump, electric motor, and all accessories. Since joined China Speedway Group in 2012, I worked in here more than 10 years, as the general manager of export department, we have established 50+ agent in different countries and areas.
As our experience and strong technical support, we can solve your issue once you have, and our chief engineer has worked in HVACR field since 1997. I am so proud of our knowlege is more and more popular not only for engineer, and for HVACR business new comer, DIY lovers. Hope you are enjoying our articles, if any question or comments just welcome to send me marketing at cn-beyond.com

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China Speedway Group is a professional HVACR products’ manufacturer and wholesaler, we customize different HVACR products and spare parts, especially refrigeration products and parts. Such as air conditioning, refrigeration equipment, cold room solution, ice machine, dehumidifier, electric motor, heat exchanger,copper coil, etc.

As worked in HVACR field since 2010, we have more experiences can provide you unique products and solutions, also will supply life-span free charge of technical support. Warmly welcome inquiry us with your sample, drawing or design, our aim is making your idea come true and benefit you. 

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