There are many possible reasons why your window air conditioner is freezing up, but the most common is dirty or faulty components, incorrect settings, and low temperatures.
Window air conditioners work by running refrigerant through a compressor on a cycle. The refrigerant, in gas form, makes the evaporator coils cold, which cools down the air that is blown over them.
However, when these coils get too cold, they may freeze. The reason why this happens to your window air conditioner is because of low airflow, faulty components, incorrect settings, and an extremely low temperature outside.
How a window air conditioner cools air
When you switch on your window air conditioner, the thermostat sends a signal to both the compressor and the fans. The compressor compresses gas refrigerant into the condenser coils at the back of your unit, where the gas turns into a liquid.
From there, liquid refrigerant travels to the evaporator coils that are close to the front panel of your air conditioner.
Here, the refrigerant is turned into a gas again, which cools down the coils. Fans blow hot air from your room over these cool coils, which is what cools down the temperature of the space.
Why is my window air conditioner freezing up?
When you know how a window air conditioner works, it is easier to understand why this type of air conditioner can freeze up sometimes.
Essentially, the evaporator coils in your air conditioner will freeze up when they get too cold, but this can happen for a wide variety of reasons.
The best thing to do if your window air conditioner does freeze is to unplug it and let the ice thaw slowly. Do not attempt to scrape the ice from the coils.
The reason why the evaporator coils get too cold and freeze up is because the moisture that usually forms around these coils when air is being cooled does not drip into the drip pan and get transported outside like it usually is. When this moisture stays around the cold coils, it will freeze.
To add to this, the air conditioner will overwork itself because the coils are not cooling air properly, which will cause the coils to be even colder and for the moisture around them to freeze even faster.
The reasons for this accumulation of moisture around the coils are as follows:
- Faulty components
- Incorrect settings
- The outside temperature is too cold
However, the main reason for a frozen window air conditioner is dirty air filters and coils that block the airflow.
The best way to prevent your air filter from freezing is to clean your filters regularly using a soft brush and lukewarm water, and to clean your coils using a coil cleaner.
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Why faulty components can cause your window air conditioner to freeze
The following faulty components may be the reason why your window air conditioner is freezing up for various reasons, such as:
| Component | Why your window air conditioner is freezing up |
| Faulty compressor | If your compressor is not moving the refrigerant properly, this could cause your air conditioner to cycle continuously, which will cause a moisture build-up |
| Low refrigerant | A leak of the refrigerant means that your unit will have to work harder to cool down air, which can make the coils too cold |
| Faulty blower fan | This will not move the air in your unit properly, which means that there is not enough warm air moving over the coils. This makes them too cold |
| Faulty drain system | If the drain system is clogged, moisture will accumulate around the coils, because it cannot be expelled |
Why the incorrect settings can cause your window air conditioner to freeze
In much the same way as having a loose or faulty fan or fan motor, which results in your window air conditioner not moving air around as it should, having your fan setting on low when it is extremely hot outside can cause your air conditioner to freeze.
When the fan setting is set too low, air will not be sucked into your air conditioner or expelled fast enough, and this will cause the coils to get too cold and freeze any moisture that has accumulated around them.
Why the outside temperature can cause your window air conditioner to freeze
Your window air conditioner is likely to freeze if you run it on the “Cool” setting when the outside temperature is already significantly low. This will cause the coils to become too cold too quickly, because there is no hot air flowing over them.
To avoid this, you can purchase a room thermometer to ensure that the outside temperature is no lower than 60 degrees Fahrenheit.
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