3 Common Causes of AC Freezing

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Depending on where you live, summer days can be blazing hot, and you rely on your air conditioner to keep your home comfortable. If your air conditioner freezes up in the summer, it could leave your house feeling hot and balmy. If you discover that the blower is still running but you can’t feel much cool air coming from the vents, your unit might be frozen over.

Your air conditioner works by expanding the refrigerant inside of the evaporator coil so that it cools down. Your system components work together to convert the refrigerant from gas to liquid and back again very quickly. When the refrigerant enters your evaporator coil, it is converted to gas and cools the indoor coil. Your blower fan moves air across the coil where the heat and humidity from the air inside your home are absorbed into the refrigerant.

Once the air is conditioned, the cooled air is circulated throughout your home, the heat is released into the outdoor air, and the refrigerant returns to start the process over again. If something goes wrong, the entire system can be disrupted. Malfunctions can cause the evaporator coil to cool too much and freeze over.

When your air conditioner freezes up, a few issues could be behind the problem. Some of the problems you may be able to troubleshoot yourself. However, several others will require the help of a qualified HVAC technician. Let’s take a look at some common causes of AC freezing.

1. Aging Equipment and Mechanical Problems.


In general, your HVAC unit should last around 20 years. With maintenance and care, you can extend the life of your equipment beyond the 20-year lifespan. However, even with proper care, as your system ages, it will begin to break down. AC components will wear out, and parts will break. Air conditioners are full of moving parts that can get stuck, broken, clogged, or begin to leak. Any mechanical issues can cause a drop in pressure allowing your refrigerant to cool your evaporator coil too much and create a frozen system.

Some of these mechanical issues are easier and cheaper to repair than others. In the case of a coolant leak, the repair will probably be a temporary solution that will require increased attention over time. If your system is older, you will probably notice that AC freezing will begin to occur more frequently. A trained HVAC professional will help you diagnose your issue and recommend a solution.

2. Dirty Evaporator Coil

While AC problems could result from mechanical issues, the problem causing your system to freeze could be as simple as a dirty evaporator coil. This is one of the most common reasons for AC freezing. Over time, the fins on the coil can collect dust, dirt, pet dander, hair, and other debris. If your coil becomes clogged or caked, the debris insulates it and prevents heat from transferring through the fins and into the refrigerant. As a result, the refrigerant continues to cool the coil, eventually reaching a temperature below freezing. When the moisture condenses on the coil, it will soon become a block of ice. An HVAC technician can clean your coil and restore your air conditioning.

3. Restricted Airflow


Your air conditioner needs a constant flow of air to work. Without adequate airflow, the refrigerant can’t transfer heat and continues to cool the evaporator coil until it freezes. Blocked or closed vents can restrict airflow enough to cause an issue. However, one of the common causes of poor airflow is dirty air filters. You need to regularly check and change your air filters to ensure adequate airflow. Proper household maintenance can help keep your system running all summer long.

If your AC freezes up in the summer, your home could become uncomfortable quickly. If you have changed the air filters in your home and are still experiencing issues with a frozen AC, you will need the help of a technician to help solve the problem.

Jamie Klein
Jamie Klein is the founder and CEO of The Green Parent. She regularly contributes articles to the site and can always be depended on to bring vegan donuts from Donut Friend to the LA office.

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