What Is Capacitor, How to Judge A Broken 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 which causes air conditioner can’t cool or heat. Today we will talk about knowledge of capacitors.

What As 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

Classification of Capacitor

Capacitors can be divided into different categories according to their principle, structure, classification, etc.

According to the different dielectrics and materials, 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

The air-conditioning capacitor is a device that starts the motor (compressor motor or fan motor). If the motor does not rotate after power is on, that means the capacitor is broken.

Once the capacitor is damaged, meanwhile the motor does not rotate, then the fan will not work, and eventually the air conditioner will not work properly.

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


Air conditioner capacitor

The Harm of Wrong Starting Capacitor Capacity

If the capacitor capacity is too large, working for a long time will easily cause the motor to increase the working current during operation, the motor is easy to burn; If the capacitor capacity is too small, the starting torque will become smaller, 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 Quality of The Capacitor?

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. For pointer multimeter testing: generally use the R × 1K row, and connect the test leads to the two poles of the capacitor respectively.

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

If the pointer does not move or the swing range is small after connecting it, certainly that the capacitor is broken.

Pointer multimeter with “1K”

3. For 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 two poles of the capacitor under test.

At this time, 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 two 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 and matching output power of compressor motor

Symptoms of Broken Air Conditioner Capacitor

1. A broken capacitor will bulge

Bulge Capacitor

2. Smoke

3. Can not operate normally

4. Indoor screen panel can’t display normally

5. The power supply can’t be discharged normally

6. Can’t heat normally

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


Air conditioner has two capacitors: the larger one is the capacitor of compressor, and the smaller one is the capacitor of the outside 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 outdoor unit of the air conditioner is constantly shaking.If you put your hand on the outdoor unit of the air conditioner,  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 after a period of time.

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

The feature of the broken capacitor of the outdoor unit: 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 air conditioner capacitor has a great influence on the air conditioner. Therefore,we don’t recommend you repair it by 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 supplier or wholesaler of air conditioner, or contact 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.

capacitor air conditioner

4. Capacitors are very important for air conditioner, so you must carefully read every detail on 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 to your life.

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