Why Is My Air Conditioner Frozen Inside?

If you’ve felt reduced airflow in your home, heard your A/C run continuously or seen a large amount of drainage around your indoor unit, these are signs your air conditioner is frozen inside.

And if that’s the case, turn off your A/C to prevent any further damage to your equipment.

Now you may be wondering, “Why is my A/C freezing up, even when it’s a hot day outside?”

We get asked that question a lot. There 2 common problems that cause your A/C to freeze:

  1. Airflow issues
  2. Refrigerant leaks

Later in this article, we’ll discuss these 2 major freezing problems. But first, let’s go into more detail about how an air conditioner freezes in the first place...

Need help right away? Call (651)-254-8117 or schedule an appointment for one of our certified A/C technicians to visit your home.

How does an A/C freeze in the first place?

You know the purpose of an A/C unit: to make your home’s living spaces cooler. But an air conditioner technically doesn’t “create” cool air, like in the way a furnace produces heat. Instead, it cools by removing heat from your home’s air.

If something’s not working right in this heat removal process, that is what’s causing your A/C to freeze up.

In a nutshell, here’s how the heat removal process works: Your air conditioner pulls in your home’s hot air and then cools it in the evaporator coil (see image above) using a fluid called refrigerant. Refrigerant absorbs heat from the passing air and carries it outside, leaving your home feeling nice and cool.

Now, if something isn’t working correctly in your system, the refrigerant can get too cold, causing ice to build up on the evaporator coil, which is what “freezes” your system.

Contrary to how it sounds, a frozen A/C doesn’t mean you’ll have a cooler home. In fact, the opposite is true: Your home will feel warm, and your A/C will waste energy because it’s running longer. Longer run times lead to system breakdowns and high energy bills, so you’ll want to fix whatever’s causing your A/C to freeze ASAP.

Let’s go into some specific causes of a frozen A/C unit...

What causes your air conditioner to freeze

Cause #1: Airflow problems

Airflow is the amount of air flowing over the evaporator coil. When there’s not enough airflow, the refrigerant in your evaporator coil will drop below freezing (32°F) because there’s not enough warm air entering the system for the cold refrigerant to absorb. 

Then, when humid air comes into contact with the coil, moisture condenses (like water beads outside a cold glass on a hot day) and then freezes. Over time, insufficient airflow creates ice buildup on the evaporator coil and limits your system’s ability to properly cool your home.

These are the most likely culprits of airflow problems:

  • You have a dirty air filter
  • Your evaporator coil is dirty
  • Your return air ducts are too small
  • Your air ducts are blocked
  • Your registers are closed or blocked
  • Your blower fan isn’t working properly


  • DIY fixes: Check your air filter, and change it if it’s dirty. In the heat of the summer, consider changing your filter once every month. Also, make sure ALL of your vents (even in rooms your don’t use) are open and that nothing is obstructing them. 
  • Call a professional: If the DIY fixes don’t work, it’s time to contact a professional cooling expert. They’ll take a look at your return air ducts for sizing and blockages. Than can also inspect your blower for malfunctioning parts and your evaporator coil for dirt. 

Cause #2: Refrigerant leaks

In a normal system, the refrigerant will be right around the freezing temperature of water (32°F). As the indoor air moves over the evaporator coil, the moisture in the air condenses on the coils, and then gently drips into the condensate drain.

But if you have insufficient refrigerant (usually caused by leaks), the pressure drops, which lowers the temperature of the refrigerant even further. The colder refrigerant makes the condensation that forms on the coils freeze. When the ice melts, you’ll notice more drainage around your indoor unit or furnace.

Other signs you might have a leak include…

  • Low airflow coming out of your air registers
  • Your home takes a long time to cool off
  • Warm air is coming from your registers
  • You hear a hissing or bubbling sound near your A/C
  • Higher electric bills


Call a professional: Only a certified technician has the tools and the expertise to check and fix refrigerant leaks. In addition to making your A/C freeze, refrigerant leaks can cause compressor failure and reduce your air conditioner’s efficiency—so you’ll want to get it fixed soon.

Need a pro to fix your frozen A/C?

On Time Service Pros can get your air conditioner back into tip-top shape. Contact us to schedule an appointment today

We’ve been serving Minnesota families since 1945.

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