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How to Fix a Frozen Air Conditioner | 5 Causes and Solutions

by vscontent on August 5, 2016

why air conditioners freeze and how to fix them

While it may seem strange that an air conditioner will freeze in the summer, it’s actually a very common occurrence. You don’t have to panic when you notice you have a frozen air conditioner.  You may not even have to call your local HVAC company. It could be a simple fix, or it could mean a call to your professional HVAC contractor. You’ll never know until you start troubleshooting your frozen evaporator coils.

As soon as you notice a frozen air conditioner, turn the unit off immediately and turn the fan setting to “on” to allow time for defrosting. Then, find out what is causing the frozen coils in the first place.

Top 5 Causes of Frozen Air Conditioner Coils

There are a few possible causes of a frozen air conditioner, namely insufficient airflow and low refrigerant level. The consequences of ignoring this problem are significant, but luckily it is an easy problem to remedy if you act fast.

1. Insufficient Airflow

One possible cause of a frozen air conditioner coil is that there is not enough air flowing over your indoor evaporator coils. The air that flows over your coils loses its heat to the coils, but if not enough air is flowing, the refrigerant gets too cold and might cause the coils to freeze.

The refrigerant that returns to the outdoor compressor will also be too cold, which could risk damage to your compressor, a very expensive part. The returning refrigerant should be warm so that it can lose heat to the outdoors. That’s how it’s supposed to work anyway.

You can tell if your indoor evaporator coils are frozen by opening up the indoor air handler compartment and taking a look.


To fix the issue, it may be as simple as replacing your air filter (clogged air filters restrict the necessary airflow for evaporator coils). Remember, you should be changing (or at least checking) your air filter every 30 days. Wait until all the ice has melted before turning your unit back on to check if a clean air filter has fixed the issue.

2. Dirty Evaporator Coils

Another cause of frozen evaporator coils inside your air conditioning system is dirty evaporator coils. This is important because the coils must be clean in order to operate efficiently. If there is too much gunk and buildup on the coils themselves, they won’t be able to absorb the heat it needs  to cool your home properly.

Make sure that your HVAC technician is cleaning your indoor evaporator coils during your yearly air conditioning maintenance! Many homeowners assume that this task is done, but it’s best to check beforehand. This will ensure that your evaporator coils remain clean of mold, dirt, and mold throughout the year.

Dirty evaporator coils can also cause clogs and debris inside your air conditioner’s condensate drain line. Once the line completely clogs, you could end up with water damage around your indoor A/C unit.

Learn more about how to prevent and clear A/C condensate drain clogs.


You may have to clean your indoor evaporator coils and replace your air filter. Although you should only clean your evaporator coils yourself if you know what you are doing, learn how to clean evaporator coils here.

3. Blocked or Not Enough Return Ducts 

If your heating and cooling system was installed properly, then you should have the proper amount of supply and return ducts. A problem arises, however, when you have blocked vents and registers.

Although you may think that closing off vents in unused rooms is a great way to save money by reducing your demand for air conditioning, you’d be wrong.


Go around your home and make sure that no supply or return vents and registers are blocked. Sometimes, these vents get inadvertently blocked by drapery, furniture, clothes, and other objects. Learn more about why you shouldn’t close off HVAC vents in the home.

4. Malfunctioning Motor

Another cause of inadequate airflow is a broken or malfunctioning blower motor. This is the part of your air conditioning system that blows the return air over the indoor evaporator coils. If there is not enough air moving over your evaporator coils, then the coil will get too cold and freeze up.


Call you local HVAC company.

5. Low Refrigerant

If you have insufficient airflow, you can possibly fix your frozen air conditioner yourself. However, if you have insufficient refrigerant, it’s probably because you have a leak somewhere in the system. In order to remedy the leak and recharge the refrigerant, you will need to call your local HVAC contractor.


Call you local HVAC company. Make sure your HVAC contractor is fixing the link as well as recharging the refrigerant.

Allowing your air conditioner to run while it has frozen parts is an irresponsible thing to do. The conditions, luckily are very preventable. Some are easy, while others require the assistance of a professional. Either way, this is an problem you want to address as soon as you can.

If the leak underneath your indoor air handler isn’t the result of frozen coils, but rather a clog in your drain line, learn how to unclog your condensate drain line here.

For more information on air conditioning maintenance and repairs, read our other blogs on the topic:

Pacific Air Systems serves homeowners all over the Lakewood, Olympia, and Tacoma area. Give us a call at (253) 292-3995 or schedule service online and we’ll send one of our qualified technicians out on your schedule.

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