9 Reasons Why Is Your AC Freezing Up & How To Fix It?

Imagine how frustrating it will be if your AC stop cooling your room on a blistering hot day. I have come across this a few times, and in most cases, it is because my air conditioner was freezing up.

An air conditioner freezing happens often, but many people have no idea about it. Please continue reading if your device is experiencing this problem. I’ll walk you through the causes and solutions to an AC freezing up, as well as how to avoid it in the future.

Signs that your AC is freezing up

Before we begin troubleshooting the freezing AC, you might want to know how to tell if your AC is frozen. Some indicators may assist you in identifying it.

1. Ice on the evaporator coil and refrigerant line-set pipe

The most straightforward way to know if your AC is freezing is to examine if there is any ice on your AC. Ice will typically form on the evaporator coil and the refrigerant line-set pipe.

The refrigerant line-set pipe is located outside of the compressor and is easily accessible, whereas the evaporator coil is difficult to reach because it is located in the indoor unit.

2. Clammy air and condensation on the windows

You may feel the room is humid even if the AC is on. This is due to the fact that your AC can’t dehumidify and cool the air when it is frozen.

Since summer always comes with high humidity, you can find condensation on the windows.

3. Your AC can’t cool the room 

When the machine is frozen, it can’t effectively cool the air because the refrigerant will not circulate between the coils and compressor as smoothly as usual. But many other issues can cause an AC not cooling.

What causes an air conditioner to freeze up?

Now that you’re almost certain it’s frozen, let’s look at why it happens. Unfortunately, there are numerous possibilities, and you must rule them out one by one.

1. Dirty air filters

dirty ac air filter

Believe it or not, there are a lot of impurities lingering in the air even though they are invisible most time. 

When your AC draws the air into it, the air will come across an air filter to remove dirt, dust, and some other substancesbefore flowing to the evaporator coil. 

The filter can become clogged over time, reducing airflow. The lack of airflow prevents the evaporator coil from warming up, causing it to freeze.

How to fix it?

Turn off your air conditioner and then remove the air filter. To remove the dirt and dust, rinse it under running water or use a soft brush. Alternatively, you can replace it with a new filter.

As an aside, you should wait until the filter is completely dry before replacing it.

2. Dirty evaporator coil

frozen evaporator coil

Even if the air filter removes the majority of the debris, some will enter the machine and attach to the coils.

When grime accumulates on the evaporator coil, it impedes heat transfer between warm air and the coil, causing it to become too cold and eventually freeze.

How to fix it?

The way to fix this problem is to clean the evaporator coil. Depending on how dirty the coil is, sometimes a soft cloth can do the work. If your AC is frozen, you should take action until the ice thaws. 

3. Refrigerant leaks

In most cases, the refrigerant remains intact in the coils, lines, and compressor. However, it may leak out over time due to factors such as metal corrosion.

When the refrigerant level is low, the reduced pressure allows the refrigerant to absorb more heat, resulting in frozen lines and coils.

How to fix it?

First, you should check the refrigerant level in your AC after the ice thaws. If it is low, you need to hire an HVAC professional to fix the leak and recharge the refrigerant. Usually, it will take less than 1 hour

4. Defective compressor

defective compressor

Don’t be too concerned! The compressor is not easy to break, but it can happen occasionally. When the compressor is faulty, it can’t effectively help the refrigerant circulate between each part and cause freezing, which is similar to the leak.

How to fix it?

Unfortunately, fixing a compressor could be costly. Therefore, replacing it is the way to go in most cases.

5. Failed fan or blower

A fan or blower is used in air conditioning systems to draw and expel air. When it fails, the airflow is reduced, causing your air conditioner to ice up.

How to fix it?

The fan is made up of a wheel and a motor. It is critical to determine which part is defective and to hire a professional to repair or replace it.

6. Wrong settings

It’s possible that nothing is wrong with the AC fan. The issue is with the settings. In hot climates, if you set the fan speed too low, your machine will overload, but there will be insufficient airflow to warm up the coil.

How to fix it?

Once the ice has melted, increase the fan speed to see if the problem has been resolved or mitigated.

7. Clogged condensate drain line

Dehumidifiers and air conditioners work at a similar principle, which will dehumidify the air through condensation. 

The collected water will be drained through a condensate drain line. When it is clogged, the water will go back into the system. When more water remains on the coil, it will ice up.

How to fix it?

Once the machine is shut off, you can find where the condensate drain line is and then use some soapy water and a brush to clean it off. 

8. Vent blockage

If you have a central air conditioner, you must ensure that every vent is clear of debris. Because a blocked vent restricts airflow, your AC, like a clogged air filter, is susceptible to freezing.

How to fix it?

The solution is naturally to remove all the items that block the vent. Inspect every vent to see if there is any furniture or appliance that happens to hinder the airflow.

9. Low temperature

To prevent freezing up, making sure there is enough heat to warm up the coil is crucial. Not only the limited airflow but also the low temperature will cause this problem.

As a result, when the temperature decreases, for example, at night, your AC may tend to ice up. 

How to fix it?

If you have central air conditioning, you can set the thermostat to a higher setting, which will turn off your AC when the temperature falls below a certain threshold.

If you have another type of air conditioner, you can use a hygrometer to monitor the temperature and manually turn it off.

What to do if your air conditioner is freezing up?

Let the ice thaw

Even if you have a rough idea of why your air conditioner is freezing, the first step is to thaw the ice on the coils and lines.

You can either turn off the machine and let the ice melt naturally, or you can run the fan only to hasten the process.

Dry your AC

You may need to clean up any water that has leaked from the machine. Furthermore, using a dry soft cloth to remove moisture from the coil and line can help your AC dry faster.

Fix the problem

Now you can try to identify and fix the problem. Chances are the problem is one of the causes I have summarized above.

Remember to check the warranty; it may save you a lot of money. To fix a compressor or fan, you should hire an HVAC pro.

How to prevent your AC from freezing again?

Not every AC will freeze up. You can take some measures to keep it at bay.

Clean and replace the air filter regularly

Depending on how regularly you use the AC, you may need to clean the air filter every month. If you have pets at home, you should increase the cleaning frequency.

Monitor the air temperature constantly

Like dehumidifiers, air conditioning systems can’t function well in cold rooms. You can change the settings on a thermostat or monitor the room temperature constantly to avoid running your AC at a low temperature.  

Make sure no vent blockage

Limited airflow is the main culprit of freezing up. Therefore, you should always ensure there is no obstacle in front of the vent.

Annually HVAC inspection 

Having an HVAC to check the state of your AC once a year can be beneficial. They can examine the state of the compressor and fan and clean the ducts if it is clogged.


This article includes almost everything you need to know about freezing up in an AC. If you don’t know why your AC is freezing up, you can check the causes I mentioned in this post and decide if you can fix it or hire a pro.

I hope this post can help you out!

About The Author

Avatar photo

Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested dozens of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

Leave a Comment