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Why Is My Aircon Unit Coil Freeze?

Freezing up of the aircon unit coil can often lead to many serious aircon issues which ultimately reduces optimal functioning and efficiency of the aircon unit. We will be going through the top and most common reasons why your aircon unit coil might be freezing up.

How to tell if my aircon unit coil is freezing?

The most obvious telltale sign would be that your aircon unit is not cooling the room as efficiently as usual. Check on the flow of air through the supply air registers. It may be a frozen aircon unit if the air is warm or if there is no air at all. There will also be a buildup of ice on the indoor or outdoor coils. If you find that your aircon unit is freezing up, the immediate thing to do is to switch off the aircon unit.

Here are some common reasons why your aircon unit coil freezes:

Dirty Air filters

Dirty air filters will hinder airflow in and out of the aircon unit. Regular and continuous airflow is needed to prevent humidity from settling onto aircon unit coils. If air is not circulating around the coils, the coils will get very cold and eventually freeze up. Moreover, ice accumulated will cause blockages in the system and reduce condensation flow out of the aircon unit.

If you have identified this problem with your aircon unit, you can consider DIY whereby you turn off the power to your aircon unit and wait for it to defrost. Meanwhile, you can purchase new air filters which can be easily found and are cheap as well. Change the dirty air filters in your aircon unit and you need to maintain your air filters to not become dirty and clogged up. Do take extra note to change your air filter regularly. 

Damaged Thermostat

The thermostat is very important in working well with your aircon unit as it regulates the temperature and controls the level of intensity the aircon unit has to work at in order to maintain consistent temperatures. When there is a sudden increase or decrease in surrounding temperatures, the thermostat will regulate the temperature back to normal levels, preventing the aircon unit coils from being extremely hot or cold.

When the thermostat is damaged and fails to control the aircon unit correctly or detects the wrong temperature, it potentially damages and wears out the entire aircon unit by working for excessive amounts of time. You might have a broken thermostat if the aircon unit is unable to keep a consistent and regular temperature or if the temperature drops all of a sudden.

When thermostats are damaged and undiscovered, the aircon unit could overwork and cause aircon unit coils to freeze. Do perform frequent checks and maintenance of the thermostat as well as other aircon unit parts to ensure that your aircon unit is in good condition to function optimally.

Refrigerant Leaks

Refrigerant is the chemical running through the aircon unit coil. The chemical helps to absorb heat by regulating pressure and temperature. It is crucial to have sufficient refrigerant in order for your aircon unit to function optimally. If the refrigerants get low or leak, the fall in pressure and temperature will cause it to absorb more heat than it is supposed to. Excessive heat loss occurs due to refrigerant lines freezing over, eventually causing the coils to freeze. 

Leaking refrigerant is harmful to the environment and illegal in some countries, therefore it is not wise to fill up the coil with more refrigerant. If you discover a leak in your refrigerant it is highly recommended to get a professional aircon servicing company in the field to repair the leak and change out the coils. It is imperative that you contact a professional aircon servicing company with minimal delay as leaking refrigerant could possibly cause a major aircon issue in the entire aircon unit as well. Click here to find out why your aircon unit is leaking.

Blocked Condensate Lines

Condensate lines in your aircon unit drain away excessive moisture built-up as a result of humidity. Excessive moisture condensed into water travels to the floor drain through the drain pipes. This makes sure that there is no accumulation of water in the aircon unit.

When the condensate line is clogged, water in the drain pipes will be stuck and accumulate and will eventually freeze resulting in the obstruction near the evaporator coil. This causes the aircon unit to cool which leads to the coil being freezed. 

The nearer the obstruction of the pipe is to the evaporator coil, otherwise known as the coldest part of the aircon unit, the higher likely the coil will freeze.

Damaged Blower Fan

The blower fan regulates the temperature of your aircon unit by circulating air around the coils, bringing in cold air from the environment, and releasing warm air.

The fan makes sure that the aircon unit does not get too cold and freeze up. If the fan is damaged there will be a lack of airflow. Condensation results due to accumulation of moisture, eventually causing aircon unit coils to freeze. 

With insufficient heat supplied, the condensate drain line will be clogged up as well due to condensation. It is thus very important to make sure that the blower fan is fixed or changed to prevent further complications in the entire aircon unit.


So, what do you do when you discover that your aircon unit coils have freezed up? Immediately switch off the power connected to the aircon unit to let the ice in the aircon unit melt and clear the surrounding water leakage if applicable.

Contact a professional aircon servicing company immediately as it is crucial that you fix the aircon issues faced immediately to prevent further complications that could potentially compromise the optimal functioning of your aircon unit in the future. Do conduct regular aircon unit servicing to prevent any aircon issues such as a leaking aircon unit


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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