6 Common Reasons Why Your AC is Freezing Up

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6 Reasons Why Your Ac Is Freezing Up

On hot days when you rely on central cooling the most, having a frozen air conditioner can be extremely frustrating. When your AC stops cooling or produces weak airflow, it leaves your home feeling uncomfortable and stuffy.

This can be confusing—why is my AC freezing up in hot weather? It’s actually very common and usually happens because of frozen coils.

The first step in addressing this issue is to figure out the cause. That way, you can fix and prevent the problem from happening again.

In this article, we’ll discuss six common reasons why your AC may be frozen, how to know the differences, and what you can do to fix it.

1. Insufficient Airflow

Frozen Ac Coil

Insufficient airflow and frozen air conditioners often go hand-in-hand due to a common underlying issue: restricted heat exchange in the evaporator coil.

The evaporator coil is responsible for cooling the air by removing heat and humidity. When airflow is restricted, it disrupts the coil’s ability to effectively absorb heat. As the evaporator coils freeze, they interact with the moisture in the air, leading to ice.

As ice accumulates, it acts as an insulator, further impeding airflow and heat exchange. This vicious cycle can lead to a significant drop in cooling efficiency, reduced comfort, and even potential damage to the AC unit.

Airflow can be restricted for several reasons. For one, your air filters could be blocked, so replacing them may fix the problem. Additionally, your AC could have blocked ducts or a malfunctioning blower fan. It’s essential to regularly maintain the system by changing filters, cleaning ducts, and ensuring fans are operating properly.

To address the issue of insufficient airflow, it begins with figuring out why the airflow stopped in the first place. If you can’t find any signs, contact a professional HVAC technician for a second opinion.

2. Low Refrigerant Levels

Low Ac Refrigerant Levels

Low refrigerant levels can also be a common cause of AC freezing up. Refrigerant and coolants play a crucial role in the cooling process -responsible for absorbing heat from the indoor air and releasing it outside. In turn, your AC unit cools your home.

When refrigerant levels drop, several issues arise. Low refrigerant means the evaporator coil can’t absorb enough heat from the air. This can lead to the coil’s temperature dropping below freezing, causing moisture in the air to freeze on its surface.

Additionally, low refrigerant can reduce your AC’s cooling capacity. When this happens, it won’t be able to effectively maintain a comfortable indoor temperature. The AC compressor is also forced to work harder, potentially causing compressor damage or system leaks.

To prevent your AC from freezing up, it’s essential to check and maintain refrigerant levels regularly. Don’t wait until it’s too late. Moreover, if there’s a leak, it should be repaired as soon as possible by a qualified technician.

3. Dirty Air Filter

Technician Removing Dirty Ac Filter

Air filters are designed to trap dust, debris, and contaminants from entering your AC system and circulating through your home. A dirty and blocked filter will reduce the volume of warm air passing over the evaporator coil. This causes the coil’s temperature to drop and potentially freeze.

The frozen layer of condensation on the coil acts as insulation, preventing it from absorbing heat from the indoor air. As a result, your AC will have to work harder to compensate and could end up malfunctioning or getting damaged.

To prevent AC freezing, remember to regularly replace or clean the air filters according to the manufacturer’s recommendations. It’s a good idea to check the air filter at least once a month to make sure it doesn’t become excessively clogged or dirty. This simple maintenance practice ensures the air in your home stays clean and flows properly.

4. Leaking Ducts

Fixing Leaking Ac Ducts

A common problem found in AC units is leaking air ducts. Air ducts are responsible for distributing cool air throughout your home. If they begin to leak, a portion of the conditioned air can escape into unconditioned areas, like your attic or crawlspaces.

Leaking ducts can cause the temperature inside your HVAC system to drop quickly. Once again, this may lead to your evaporator coil mixing with condensation and freezing.

When this happens, your AC will work less effectively. Leaking ducts often cause energy bills to spike, so it’s important to make sure that the ducts are sealed properly to help keep your energy costs down.

In addition to wasted energy, they can also lead to uneven heating or cooling in different areas of your home.

If you suspect this may be your issue, check your air ducts. If you find any leaks or cracks, schedule an appointment with an HVAC professional to get them sealed up as soon as possible, since the problem won’t go away on its own.

Moreover, you should inspect your air ducts regularly and make sure that all the connections are secure. Regular duct inspections can improve the overall AC system efficiency and prevent future freeze-ups.

5. Broken Thermostat

Broken Thermostat

The thermostat serves as the control center for your heating and cooling system. But if your thermostat breaks, your AC won’t be able to accurately register the temperature in your home and adjust accordingly.

This can lead to temperature inconsistencies. In some cases, it may cause the AC system to run continuously or not at all. What’s more, if the thermostat fails to signal the AC to cycle off, your evaporator coil becomes excessively cold, eventually causing freezing.

If you think your thermostat may be the problem, it’s a good idea to call a professional technician to come and take a look. They’ll be able to quickly and accurately diagnose the issue, as well as get it back to working condition.

A faulty thermostat should be repaired or replaced promptly. That way, you won’t have to deal with inconsistent temperatures or the frustrations of a frozen AC unit.

6. Faulty Blower Fan

Faulty Ac Blower Fan

Sometimes, you can exhaust all options and still wonder: why is my AC freezing up? Well, one other reason could be a faulty blower fan. The blower fan is responsible for moving air through the HVAC system. If the blower fan is not functioning correctly, it can disrupt the airflow over the evaporator coil.

A faulty blower fan might not deliver enough warm air over the coil, causing it to drop below freezing and cause ice to build up. If the fan is running too slowly or not at all, it can cause the AC system to overheat and potentially shut down.

To prevent this issue, check the fan motor periodically to ensure it’s running smoothly and efficiently. A professional technician can also repair or replace a damaged blower fan to get your AC running like normal again.


Keeping a cool and comfortable home is a necessity. If you notice that your AC is frozen or working less effectively, try to get the issue resolved as quickly as you can. That way, you can prevent further damage and maintain an indoor temperature that’s just right for you.

Now that you know the main causes of a frozen AC, you are better equipped to diagnose the issue and fix it accordingly. However, if you are still having trouble with your AC freezing up, contacting a qualified professional may be your best bet. If you’re in Florida, B & J Heating and Air Conditioning has you covered. We have a team of caring and expert technicians who can quickly get your AC working like new. Reach out to us call 727-295-3051 if you’d like to book an appointment or have any questions

Why Is My Ac Freezing Up Infographic
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Ty Schaedel

Ty has been involved in the HVAC industry since he was about 12 years old. He worked with his dad and his uncle in Indiana, where they had their business. Over the years, he has done some construction work, but his heart was always with HVAC work. He made the leap and got licensed, and opened his business in July 2018. Ty’s commitment to you is Old School Customer Service, to always treat you fairly like he would want a member of our family treated.
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