Why Does Your Air Conditioner Freeze Up? 6 Common Causes

Is your air conditioner freezing up? This article will let you know the common causes of this issue. An air conditioner (AC) is a system that is used to cool down an apartment, house, or other closed places. The system removes heat from the area and transfers it to another place outside the area. Besides, the cool air can be circulated in a wide area via ventilation.

The most significant difference between air conditioners and heat pumps, which operate similarly, is the cooling cycle that an AC has. For the AC to cool, it follows some stages. The stages include absorption of heat from the room by a cold liquid in the evaporator. The refrigerant transforms the phase to gas and raises its temperature by moving it through the compressor, the refrigerant’s passage, the condenser coil, and moving heat outside from the refrigerant. For your next Air conditioner repair in Toronto, connect with Smile HVAC.

However, the system sometimes freezes up, an issue that obviously affects its effectiveness. Have you ever suspected that your AC unit has a problem and check its indoor part only to find that it is completely covered with thick ice? Air conditioners operate when there is a warm temperature in a place, so what could be the freezing cause? Keep on reading to learn the main causes of an air conditioner freezing up.

Why Is My Air Conditioner Freezing Up?

No or Low Airflow

Wondering what makes your air conditioner freeze up? It can be due to low airflow. If the airflow from the equipment to the room or the room to the equipment is limited, there is a restriction in the thermal energy exchange between the unit and the room. As a consequence, cool air is concentrated on the evaporator fins and coil. Therefore, it drops the temperature around the coil and fins. This leads to the formation of ice. It will increase in size leading to the formation of more ice. As a result, the air conditioner freezes up. If there is not enough air, the heat is too limited to prevent condensation.

Low refrigerant

If the AC doesn’t have enough refrigerant or there’s a leakage for some time, the system’s saturation point will decrease. As a result, it would only require a lower temperature to vaporize the condensed liquid that has already been compressed by the compressor in the evaporator. This case means that the cooling coils’ temperature is relatively low compared to the cooling temperature of the usual design. The moisture that is gathered from the air will turn into ice quickly because of the cold weather. Instead of the moisture cooling to the point of turning into water and moving to the condensate drainage pan, it gathers at the evaporator fins and coils and forms ice on them. As a result, an ice block will be formed on the evaporator coil and fins.

Damaged blower fan

Wondering why is the air conditioner freezing up outside the unit? The function of a blower in the air conditioner is to remove cold air while absorbing warm air. When air cools inside the AC, the air becomes denser, and its movement is restricted. The effectiveness of the air conditioner is creating cold air. It depends on the machine’s proper airflow and air pressure balance. However, when operating normally, the fan can get damaged. This will affect airflow in the air handler. Evaporation and drainage of the water droplets will not be efficient because of increased condensation on the coils. Apart from restricting the proper flow of hot air, the broken fan can also lead to the refrigerant line’s freezing. Also, the problem can extend to the outside environment.

Blockage of air-cooling coils

Another reason for the air conditioner freezing up could be a blockage of the air cooling coils. A concentration of dirt, dust or other substances can block airflow. It leads to the air conditioner freezing up outside the unit. When there is not enough airflow in the coils, the unit’s cooling capacity reduces. Hence, the air conditioner is freezing up. Another challenge associated with the coils’ blockage is removing the accumulated water in the coils.

Drainage issues

The air conditioner’s condensation drains are typically located outside. In case the coils are broken, and the air conditioner becomes frozen, the ice formed will eventually lead to blockage of the drain. Although the unit may continue to operate, it will consume more electricity and maintain enough coolness. Apart from freezing, blockages can destroy the compressor and other significant parts of the air conditioner.

Mixture of problems

The mixture of problems is what makes your air conditioner freeze up. When your air conditioner has a low refrigerant amount, for instance, the unit might have one or two fewer pounds of it; you might fail to notice some freezing up in the unit. However, when this problem is combined with a thermal expansion valve, ice may be formed. After a short time, the coil will be fully frozen. Also, another issue that one should be careful about is a malfunctioning thermal expansion valve. It is common for air conditioners that have lasted for more than fifteen years. The thermal expansion valve’s function is to act as a traffic light for the refrigerant by regulating its flow. However, if the valve doesn’t work properly or becomes sticky, the formation of frost can occur in the system components of the air conditioner.


In conclusion, air conditioners assist in cooling a place. However, its system might freeze at any time, as a result, affecting its work. Regardless of the reason for the freeze in your AC, you should not handle the process carelessly by applying heat on the frozen parts. You need professional help to fix your unit. Consistent maintenance check-ups and good filter care can assist in limiting the chances of freezing in the AC. And if your AC unit is frozen, you should start by turning it off. A frozen unit can be an indicator of a severe challenge. Continuing to use your AC in that state can only worsen the situation.