In-Depth Guide to Aircon Capacitor

All the way from the power company to your aircon, there are many stages at which an unexpected electrical surge can damage your system. The capacitor is one of those critical stages. This article will explain what a capacitor does and how you can find out if it’s faulty or not.

You’ll also learn about some common problems that can cause capacitors to fail, as well as their lifespan and replacement cost information, so you know when it’s time for a new one!

What Is an Air Conditioner Capacitor?

It is also known as a run capacitor; these are small objects that are cylindrical in shape. Its primary function is to send a jolt of power to the motor, which powers the AC system. Therefore, it is an electronic component that stores charge in an electrostatic field. When a person witches their unit ON, it delivers an electric boost needed to turn the unit and provide continuous power.

What Is the Function of An Air Conditioner Capacitor?

Often found on a printed circuit board, the primary function of a capacitor is to smooth out energy delivered to the unit and prevents power (energy) interruptions. As such, if a capacitor fails, all relevant parts will not function smoothly and sometimes fail also.

It also helps store energy which is then released during start-up. It functions similarly to when a person is trying to start up their vehicle. For this reason, capacitors are generally used in three main components in an air conditioning unit. These are: –

  • The compressor motor
  • The blower motor
  • The outside fan

How To Identify a Bad Capacitor In An Aircon?

When a capacitor fails, it will indeed affect other systems within the AC. Below are the most common signs of a bad capacitor in an AC: –

  • The AC is not turning ON
  • AC shutting itself off
  • Harming sound coming from the unit
  • The AC takes some times to start
  • The AC is not blowing cold air

What Will Happen If an AC Capacitor Fails

The major problem many will face is ‘Hard AC Start’.

In other words, the compressor of your unit will find it difficult to start when it has been turned ON.  In some cases, it will begin to quickly but shut OFF by itself after some time. However, although a failed capacitor will make it hard to start the unit, it is essential to know that other factors may cause a hard start.

What Causes AC Capacitor to Fail?

The main primary cause of a capacitor failure is age (or when you run the AC for a very long uninterrupted time). In fact, capacitor failure is more common in tropical areas like Singapore, where the temperature is warm and humid. The hot climate combined with the heat generated when the unit is running causes an Air Conditioning unit to fail or malfunction.

Other causes include short circuits in the cooling system, lightning strikes, power surges, and an overheated circuit.

Is It Possible to Run an AC with A Bad Capacitor?

The truth is that most motors cannot run without a capacitor or with a bad capacitor. Remember, the primary use of a capacitor is to support the motors by helping them start and run. In a nutshell, it will affect your system’s motors in one way or another. Therefore, if you notice any motor in your unit is not spinning, most likely the culprit is a failed capacitor.

Is It Possible to Replace an AC Capacity By Myself?

The short and direct answer is YES! Only if you know what you are doing and you know how to diagnose a capacitor failure.  The good news is that you can buy a replacement capacitor at your local store. After this, the next step is installing it.

How do you do this safely? Well, to do it safely and correctly, please follow the following steps: –

  • First: – Shut OFF the power to the unit from the breaker panel
  • Second: – Access the capacitor by unscrewing the side panel of the conditioning unit.
  • Third: -Locate the failed capacitor. However, before you uninstall it, make sure that you have discharged it to prevent an electrical shock. 
  • Fourth: – Dismount the capacitor and connect the newly bought capacitor carefully. Remember, as you are doing this, make sure that you have noted the way wires were connected. If you are not sure how to connect, consult your manual. 
  • Fifth: – Screw the panels back and switch on the power to the unit.

Watch this video if you want to find out how to change the capacitor at the outdoor unit.

How Much Will It Cost Me to Replace an AC Capacitor?

The cost ranges from $140 – $240 in Singapore. Nevertheless, the cost will be affected or influenced by several factors, such as the cost of the unit, brand, model, labour needed, the capacitor itself, and others. The average cost is $170, but in some high-end AC, the cost can go up to $300.

How To Identify the Capacitor My AC Needs?

  1. The first thing to do is to consult your manufacturer’s manual to see if the AC capacitor capacity and model have been included – If it has not, try contacting the manufacturers and asking them.
  2. In most cases, you will find a rating has been included. If this is not possible, multiply the working power of the motor, which is in Kilowatt, by the power factor in table 1 in the resource below. This will give you the exact size of the capacitor needed.
  3. Multiply 2,650 by the full load Amps and then divide the amount you get with the supply voltage. Remember, both the full supply voltage and load amps can be found in the manual. The digits you get will be in Microfarad, which is the unit used to measure capacitance.  You may round up or down the figures by 10 percentages to get values known as tolerance values of the capacitor.

NOTE: if all this is complicated, it is wise to allow a professional to help you or offer this service to you.

What Is the Difference Between Run Capacitor And Start Capacitor?

Run capacitors are the most common types of capacitors found within a unit. They work by storing energy, which is then used to turn the motors. As such, without run capacitors, AC fan motors will not turn.

Start capacitors are not that common but play a critical role in an AC unit.  Without this capacitor, the unit will not start at all. The primary function of a starter motor is to offer that initial energy needed to start up a unit. That is because a lot of torque is necessary to start an AC system, and these capacitors will have higher capacitance compared to run capacitors.

It is important to note that Air conditioners come with dual-run capacitors. One of the capacitors will deliver the needed jolt to the fan motor, while the other will send the required power to the compressor.

Clearly, capacitors play an important role and must be maintained regularly to prevent failure. To do this, you must perform regular diagnoses via a yearly maintenance contract.


The article detailed everything you need to know about aircon capacitors. We hope it helps! If you have any questions, don’t hesitate to contact us. Our team of experts can help you find the right solution for your needs and budget.

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