Aircon Capacitor Essential Guide & FAQs

From the power stations to the air conditioner, there are many different spots where an unexpected power surge in the power supply can cause damage to your air conditioner. One of these stages is the capacitor. In the following article, we will take a closer look at what capacitors do and how you can make sure the capacitor in your AC unit is working properly.

We will also cover some of the most common problems that capacitors face, how long you can expect your capacitor to last, and how much the replacements will cost. All this information will help you keep your AC unit in excellent condition for as long as possible.

What Is an Air Conditioner Capacitor?

Also called the “run capacitor”, these small electrical components often have a cylindrical shape. The primary function of a capacitor is to supply a jolt of power to the motor that powers the electrical system. A better way to think of the capacitor’s function is by storing a measure of power delivered to the system. When the AC unit is powered on, the capacitor will boost power to activate the system and keep it turned on.

What Is the Function of An Air Conditioner Capacitor?

The capacitor is found most commonly on the printed circuit board and has the primary function of smoothing out the electrical current provided to the unit and prevents power surges. So, if the capacitor fails, the system will not function smoothly and will be at risk of a major interruption.

The capacitor will also store a measure of energy which allows the unit to start up properly. Starting up an air conditioner is a lot like starting up a car in this regard. For this reason, capacitors are mainly applied in three parts of the air conditioner.

Related Read: Essential Guide to AC parts

How To Identify a Bad Capacitor In An Aircon?

When the capacitor within the air conditioner fails, the entire system will react poorly. Here are some of the most common indications that the AC’s capacitor is not functioning well.

  • The AC fails to turn ON
  • AC shuts off by itself
  • The strange sound coming from the unit
  • The AC takes a long time to start
  • The AC doesn’t blow cold air

What Will Happen If an AC Capacitor Fails

The biggest problem that will come from a failed capacitor is that the AC will “hard start”.

This means that the air conditioner will have a hard time starting up even when it has been turned on.  In some cases, it may turn on but will soon begin to shut off. Nevertheless, even though a faulty capacitor can make it difficult to start the AC, there are a few other reasons this can happen.

What Causes an AC Capacitor to Fail?

The main reason that a capacitor will stop working is age, or if your AC is typically run for many consecutive hours with no interruption. This is why those air conditioners that are used in especially hot or tropical environments, like Singapore, are more prone to capacitor failure.  The hot climate and moisture in the air combine the heat generated by a constantly running AC unit, which can cause a malfunction early in the air conditioner’s lifespan.

Other causes for a malfunctioning capacitor include power surges, lightning storms, short circuits in the cooling systems and an overheated circuit board.

How to Test an AC Capacitor?

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

Actually, most motors can’t function at all or can’t function well with a faulty capacitor. Never forget that the primary function of a capacitor is to help the motor startup and run properly. If the capacitor is not working, you can rest assured it will affect the functionality of the motor in some way or another. Therefore, if you see that your air conditioner’s motor is not functioning properly, you can safely assume the capacitor is at the heart of this issue.

Is It Possible to Replace an AC Capacity By Myself?

Changing a capacitor in an AC unit can be done by just about anyone. But it is important to have some experience in this task and know that the capacitor is the problem. A new capacitor can be purchased at your local supply store, and after this, the procedure is fairly simple.

Follow these instructions to remove and replace your capacitor safely.

  1. Shut off the power to your Air Conditioner
  2. Access the faulty capacitor by unscrewing the side panel
  3. Locate the failed capacitor. But before you uninstall it, you should make sure that it has been fully discharged of its electrical power to avoid the risk of electric shock.
  4. Dismount the old capacitor and connect the new one exactly as you saw the old one was connected. If you are unsure how to accomplish this fairly simple task, you can consult the owner’s manual for more information.
  5. Return the panel back to its place and switch the power back on.

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

The cost for replacing the capacitor of your AC unit will run between $140 – $240 in Singapore. But this cost can be affected by a variety of factors, including the brand of air conditioner, the model, and the amount of labour needed. The average price for this replacement will be about $170, but for a high-end AC, the cost will go up as high as $300.

How To Identify the Capacitor My AC Needs?

  1. The first place to check for the correct capacitor for your AC unit will be in the owner’s manual; if you can’t find any specifics, you should contact the manufacturers.
  2. Most often, you will find the description provided in the owner’s manual. Still, if not, you can find the exact size of the capacitor by multiplying the working power of the motor, in kilowatts, by the power factor in the resource below.
  3. Multiply a full load of amps by 2650 and divide the product by the supply voltage. These figures can all be found in the owner’s manual. The answer you get will be the Microfarads, which is the unit of measurement for capacitance. You can round this figure up or down 10% to get the tolerance for your capacitor’s value.

If this seems a bit complicated to you, you should probably get help from an experienced AC technician.

What Is the Difference Between Run Capacitor And Start Capacitor?

Run capacitors are the most common type of capacitors found in an AC unit; they function by storing energy and using this to power motors. Some components of the AC will not function without the run capacitor.

Start capacitors are not as commonly found in AC units, but they play a crucial role anyway. Without the start capacitor, the AC unit will likely not startup at all. They provide that initial burst of power required to start up the unit. These start capacitors will often have a higher capacitance than the run capacitor. Find out more here.


This article covered all the essential information you need on capacitors, and we hope you have found it very helpful. If you have any further questions about this, don’t hesitate to contact our experienced professionals right away. Our team of experts can help you find the right options for your needs.