How to Keep a Window Air Conditioner From Freezing Up

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During the warmer months, knowing how to keep a window air conditioner from freezing up is essential. If it does happen, the unit won't work properly, and you and your family may find yourselves in a bad position. Worse yet, a dysfunctional air conditioner can cause water damage to your ceilings and walls, and the unit itself can end up temporarily broken or even ruined for good.


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Why Window A/Cs Freeze Up

The three main reasons why window air conditioners freeze up are insufficient airflow, not enough refrigerant and mechanical failures. When the mechanical components malfunction, this can lead to decreased temperature and pressure. These issues can cause condensation to accumulate on the coils, which then causes them to freeze up.


Turning the temperature on an A/C unit down too far can also cause this issue, but this is just user error. Start by raising the temperature on your air conditioner and then proceed with proper maintenance.

The most obvious sign that a window air conditioner is frozen is when you see that the evaporator coils are covered in ice. Once you detect this problem, you need to take action as soon as possible. Repairing it can be a DIY project unless the damage is too extensive.


The best way to prevent this from occurring is to learn how to keep a window air conditioner from freezing up in the first place. Routine maintenance and upkeep of the unit are essential and can save you a lot of money in the long run.

Cleaning Evaporator Coils

Clean evaporator coils are important for preventing air conditioner freeze-ups. To perform this routine maintenance on your window A/C unit, you should gather a 4-in-1 screwdriver, an air conditioner fin tool, rags, a shop vacuum and leather work gloves. Also get some A/C coil cleaner, a nylon bristle brush, electric motor oil and an all-purpose household cleaner.


Unplug the unit and snap off the plastic trim panel/filter holder. Then, have a friend help you remove the unit from your wall or window. For window units, remove its mounting frame or case using the screwdriver. Wearing the gloves, use the fin comb to straighten out any bent fins. Vacuum up any dirt and debris from the coils, and spray the coil cleaner on both coils. Use the brush to clean up any heavy buildup, brushing in the direction of the fins.


More A/C Maintenance Tips

You should also regularly clean off the fan blades using the household cleaner and rag. Some fan motors have oiling ports so you can remove their tops and add in a couple of drops of the motor oil. This will help with the airflow.

Another way to keep an air conditioner in your window from freezing up is to add refrigerant when it's needed. This should only be done after a thorough cleaning though. Start by holding up a thermometer next to the unit for a few minutes to see how cold the air is that's blowing out. Then, get a temperature reading on the air that's being drawn into the A/C unit. If the difference between these two numbers is less than 15, you can try adding some refrigerant.

Wall air conditioner units are built differently, so you'll need to follow the manufacturer's instructions for adding the right kind and amount of refrigerant. Sometimes, wall air conditioners also need to be recharged, but this is a project better suited for those who have HVAC experience. When a window air conditioner unit is frozen, not cooling properly or needs regular maintenance, the best choice may be to call in the professionals.