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Identifying and Replacing A Faulty Aircon Unit Capacitor

For an average homeowner, the idea of a bad aircon unit capacitor can be daunting. If you are not familiar with the parts of an aircon unit, or you don’t feel very mechanically inclined, worry not. A capacitor is a small component of your aircon unit that sends pulses of energy to the motor to help it start up the fan. When a capacitor goes bad, you will still hear your unit kick on and off, but it won’t blow cold air because the fan can’t start spinning.

An aircon unit capacitor also helps keep the aircon unit running. In Singapore which is known to have the hottest or most humid weather, most aircon units come with three motors, and the three motors are powered by the use of an aircon unit capacitor.

Therefore, if the aircon unit capacitor is not working properly, then your aircon unit will not function optimally and offer satisfactory cooling. In other cases, the motors will not start and the aircon unit will not work. In other words, the failure of aircon unit capacitors will result in the breakdown of aircon units.

What causes aircon unit capacitor failure?

The most common reason for aircon unit capacitor failure is being overworked, that is, running the aircon unit for extended periods of time. This results in overheating of the aircon unit and so, blowing up of its fuses and capacitors.

This is most common in countries with tropical or hot climates such as Singapore. A blown-up capacitor is easy to notice. An aircon unit with a blown-up capacitor produces a humming sound and the fan no longer runs.

Diagnosing a faulty aircon unit capacitor:

The best news of all is that diagnosing a faulty aircon unit capacitor doesn’t necessarily require a lot of skill or knowledge. There are a few simple tests you can perform to determine whether or not the capacitor is at fault.

The simplest test is to wait until your condenser unit kicks on, and then use a stick to gently push the fan blades around. If the motor kicks in and the fan keeps running, it’s a sure sign that the starter capacitor is not sending the necessary power pulse to get the fan going.

When to repair or replace aircon unit capacitors?

An aircon unit capacitor can be damaged by heavy power surges, but more often they simply wear down and lose their ability to hold a charge. When a start or run capacitor begins to fail, one of the following symptoms may occur:

1) As a capacitor begins to wear out, it may make an audible clicking sound within the cabinet. If you hear this, replace the capacitor immediately, as the aircon unit motor itself could burn out if the capacitor fails to start the motor.

2) When a capacitor dies completely, the aircon unit motor will try to come on but may make a humming sound rather than fully starting up. It is easy to hear this malfunction. Again, this is a sign that immediate replacement is needed.

3) When the capacitor attached to the compressor starts to weaken, it may cause a “hard-starting” condition in which the aircon unit struggles to turn on but then shuts down again almost immediately. Replace the capacitor immediately, because this situation puts a huge strain on the compressor and other parts of the aircon unit.

The following are steps that you can follow to replace a bad capacitor:

1) Put off the condenser

A condenser is the part of the aircon unit box that stands outside. Have your protective gear on, find the condenser, turn it off and use a tester to make certain that there is no power in it.

2) Open the access panel

After ensuring that the condenser has no power in it, go for the access panel. It usually has a label that has an electrical warning on it. Loosen the screws and open them.

3) Get a new capacitor

After you open the access panel, you will find the faulty aircon unit capacitor. You should easily find it as it has a sticker and is shaped like a can. Write down the technical data of the faulty capacitor. Such data include its load voltage, tolerance, capacitance, and such. Use this data to buy a new capacitor with the same characteristics. In doing this, the shape or size of the new capacitor does not matter; the performance properties do. The shape and size will not affect its operation.

4) Check the connections of the faulty aircon unit capacitor

Have a look at how the faulty capacitor is connected and note down the connection. The new capacitor may need to be connected in the same way.

5) Connecting the new aircon unit capacitor

When connecting the new aircon unit capacitor, you should disconnect all wires from the bad capacitor and join them to their respective spots on the new capacitor. To avoid confusion, you can do this one wire at a time. That is, you disconnect a wire from the old capacitor, and then connect it to the new one before proceeding to the next wire. After you have connected all the wires, mount the new device in place and make sure that it is stable. Also, make sure that the connections are firmly fixed at their places.

6) Check the condenser

Switch on the thermostat and watch the operation of the condenser. If all is working well, then you may cover the condenser. You can now use the aircon unit once again. The above information will help you discover when an aircon unit capacitor goes bad before the motor blows out. The information will also help you replace an aircon unit capacitor. However, it is always good to remember that you should protect the aircon unit capacitor to prolong the life of your aircon unit. The indeed hot climate in Singapore and the heat given out by extra-hard working motors make aircon unit capacitors break down. Therefore, it is recommended that you should not run the aircon unit for extended time periods.


It’s always a good time to talk about the common issues that aircon units have. This way, you’ll be able to spot if there are problems with your unit or not and prepare for its replacement accordingly. If you require our aircon servicing services, Whatsapp us at +65 9222 4141 for a fast and transparent quote.

338 Aircon Servicing Singapore provides an extensive range of Aircon Services including Aircon Servicing, Aircon Repairs, Aircon Installation of the best aircon brands, Chemical Overhaul, Gas Top-up, Aircon Leaking Water, and Aircon Not Cold Fix, and more. We have a team of professional technicians who are equipped with vast knowledge and experience in the Aircon industry. 

We have over 15 years of experience in dealing with aircon works and have completed thousands of aircon works for both residential (Landed, Condo, and HDB) and commercial. We are a highly recommended Aircon Company in Singapore, with many delighted customers and reviews over the years on Google and Facebook.

WhatsApp us at +65 9222 4141 for a transparent quotation and honest pricing for all your aircon needs or Call us at +65 9222 4141. We offer a fast and efficient service to serve any of your aircon needs! 


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