Why Is My Aircon Not Cooling Properly?

Nothing is more disappointing than finding out that your aircon is not cooling properly during a particularly hot day.

There are a lot of reasons why your aircon is not blowing cold air as it should. The underlying causes range include mechanical issues and factors that are not in your control.

In this article, we will discuss the reasons why your aircon is not cooling, and how to troubleshoot this problem.

Non-technical reasons why your aircon is not cooling properly

The following are the most common non-technical reasons why your aircon is not cooling your room properly.

Aside from the first one, these causes are easily solved and do not indicate any form of damage or defect with your unit.

Undersized unit

We are not talking about the physical dimensions of the air conditioner; what we are referring to is its cooling capacity.

The cooling capacity, expressed in kilojoules/hour (kJ/hr), British Thermal Units (BTU), and Horsepower (HP), is used to measure the amount of heat your aircon can remove from the air per hour of use.

An under-powered aircon will still blow cold air to your room. However, it will struggle to cool the entirety of the room. Apart from cooling problems, it will also use up more energy and will strain your unit’s motor.

We’ve written about the correct method to find out the proper size of the aircon for your room. Check it out!

Unfortunately, the only way to solve this issue is to sell your current unit and then purchase an aircon with the appropriate cooling capacity. This is why proper research should be done when buying a new air conditioner.

High ambient temperature

While an air conditioner’s primary job is to cool you down during hot days, it may fail to do so if the ambient temperature is too high to contend with.

Yes, we know, it is annoying. But be glad to know that this is only temporary and your aircon is not broken at all.

Sunlight on the outdoor unit

Sunlight is another source of heat that your aircon should not deal with as this can throw its temperature regulation out of whack. The outdoor part of your air conditioner should be kept out of direct sunlight.

What if you have no other choice but an area with direct sunlight? Consider placing an awning for your AC as seen from this video from the Land To House YouTube Channel.

Technical reasons why your aircon is not cooling properly

If any of the above three reasons are not probable in your case, the problem may be due to improper maintenance and/or factory defects.

Some of this causes have a relatively simple troubleshooting procedures that you can try on your own. You can always call a technician when things get too complicated.

Dirty air filter

As the aircon sucks indoor in to its body, the air goes through a dust filter so that it won’t blow out dirty air in to the room.

If not properly maintained, the air filter will accumulate a thick layer of dust. This air filter will hinder air flow over the evaporator coils, preventing them from cooling properly.

The fix: Take off the air filter (it can be accessed by opening the air intake panel of the aircon) and clean it. Ideally, you should clean your aircon’s air filter once a month. At the bare minimum, you should clean it at least once every three months.

Dirty condenser coils

The condenser coils transfer the heat from the air to the outside environment. If this gets too dirty, the heat will not dissipate properly. This can make the air being blown to your room warmer than usual.

For window type ACs, these coils are the ones hanging on the back. For split type models, the condenser is located in the outdoor unit.

The fix: clean the condenser coils. You can DIY this if you know your way around air conditioners. If not, you can call a technician to do it for you.

Frozen evaporator coils

The evaporator coils are responsible for the “absorption” of the warmth from the indoor air (this warmth is then dissipated by the condenser coils). In short, the evaporator is the part that actually produces the cold air.

Since this is the coldest part of the aircon, it has the tendency to freeze over from time to time.

You might think that a layer of ice on the evaporator will make the air colder – this is not the case. The layer of ice hinders the evaporator from absorbing the warmth of the air. This will make your aircon blow warmer air than usual.

The fix: first of all, clean your air filter as this is one of the causes of frozen evaporators. Cleaning the evaporator itself can be tricky – call a technician if needed.

Broken blower fan

After the air passes through the evaporator, it goes through the blower fan which distributes the air to your room.

If the blower fan is malfunctioning, you will not feel any wind coming out of the aircon’s louvers.

The fix: the blower fan may have frozen over (like your evaporator) – you can clean it yourself, or have a technician look into it. If it is broken, you should have the part replaced.

Freon leak

Air conditioners work by transferring heat from inside their compartment to the outside by continuously evaporating and condensing a refrigerant gas known as Freon in a closed system. However, Freon can leak given the right (or wrong) circumstances.

Freon is a relatively odorless and colorless gas, so it is hard to know if it is leaking from your aircon. However, your air conditioner will begin to show symptoms when it does leak – like weak cooling.

The best DIY way to know if your aircon is leaking its refrigerant gas is to apply a soapy water solution to the condenser coil and evaporator coil. If the soap is bubbling up, it means that your unit is leaking Freon.

The fix: have your unit’s refrigerant recharged by a professional technician, as it is complicated and can be dangerous when done incorrectly.

Broken compressor

The compressor is called the “heart” of the air conditioner as it pumps the Freon (the blood in this case) throughout the coils embedded in the aircon.

Needless to say, if the compressor is not working, your AC will not produce cold air as it should.

If you’ve switched on your aircon but do not hear any whirring sound or any movement at all, this may be the case.

The fix: Honestly, don’t. Just replace your aircon altogether. Not only does the compressor cost as much half of the price you bought the aircon for, the labor cost is also significant owing to the complicated nature of the job.


As you’ve seen, there are a lot of reasons why your aircon is not cooling properly; most of these causes can be prevented by performing regular maintenance for your air conditioner.

Have your air conditioner routinely checked by a technician at least once a year, and clean the air filter at least every 3 months on your own.

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