Air Conditioner Freezing Up? Here’s What to Do Right Away


It seems to happen on the hottest day of the year - you realize your air conditioner isn’t cooling off the house - in fact, it might even be blowing warm air - so you set off to try and figure out why. Eventually, you find that your air conditioner has frozen. But how? And why? If your AC is freezing up, there are some things you should do right away. 

This guide will explain why your air conditioner is freezing up and how you can prevent it in the future. The information you’ll learn here will prevent damaging your air conditioning system and get you cooling back off in no time!

How can you tell if your AC is frozen?

The obvious sign that your air conditioner is frozen is that you actually see frost or ice on the evaporator coils on your interior unit or on the compressor outside. Other signs that your AC is frozen are:

  • If the vents are blowing warm or no air;

  • When you can see condensation formed on the indoor unit;

  • If condensation appears on the exterior condenser unit.

What causes an air conditioner to freeze?

A lack of airflow is the number one reason an air conditioner freezes up. To get technical for a minute, if there isn’t enough air moving through the system to transfer the heat, the refrigerant will freeze in the coils instead of converting to gas. 

While lack of airflow is the root of the problem, there are many things that cause a lack of airflow:

Clogged air filters

When is the last time you changed your air filter? An accumulation of dust and dirt on the filter can slow or even block airflow. This is one of the most common reasons AC units freeze up. 

Air conditioner freezing up? Check your air filter.

Blocked supply and return vents

Check your air vents - both the vents that supply your cool air and the return vents. Make sure they aren’t blocked by any furniture, curtains, or other belongings, causing insufficient air flow. Also, it’s not a good idea to close more than two or three supply vents. People think they’re saving money by not cooling off unused rooms, but closing off too many vents actually restricts airflow and is bad for the air conditioning system.

Damaged AC blower fan

Go outside and look at your air conditioner’s condenser. If the blower fan isn’t turning, that could be the problem. A damaged or broken blower fan can cause ice formation. This is a repair that should be handled by an HVAC professional.

Dirty AC coil

If dirt gets caked onto the AC’s evaporator coil, airflow will become restricted and it will eventually freeze up. No matter how clean you are, inside air contains dust, it travels through the air ducts, most of it gets trapped by your air filter, but some of it gets through and it will make it to your coil. Over time it will get dirty. That’s why it’s so important that you have regular maintenance checks and system cleanings done by your local HVAC pro.

Collapsed air duct

Air ducts are the main highways in which air flows through your home. If one of them gets damaged or collapsed, airflow will be blocked which could lead to a frozen air conditioner, among other things. 

Refrigerant Leak 

Low refrigerant due to a leak could cause your air conditioning unit to freeze, but this is something you’ll want to leave for the professionals. Air conditioners are closed systems, so you should never have to add more refrigerant. If your system is low, that means there is a leak somewhere.

When you realize your AC unit is frozen, do this immediately!

Frozen air conditioners are common and frustrating, but it could just be a one-time thing. Save yourself some money (and hopefully save your air conditioner) by following these steps. 

Before you call for help, do this:

1. Turn off your air conditioner

Using your thermostat, turn the air conditioner off. Then, turn the fan on (not “auto” but “on”). This will stop the cooling system but will blow the warm air through your system and speed up the defrosting process. 

2. Wait for the system to defrost

Give the system time to defrost completely. Depending on how hot it is outside and how frozen solid your air conditioner is, this could be anywhere from a few hours to a full day. Don’t attempt to use your air conditioner until it’s completely thawed or you could risk damaging your system.

3. Replace your air filter

Unless your filter is clean, replace your dirty air filter with a brand new, clean one. 

4. Check your vents

Make sure your return and supply vents are clean and free of any furniture, curtains, or anything else that might be blocking them. Check all the rooms to make sure none of the vents have been closed.

5. Turn your HVAC system back on

When you’re certain that the system is completely defrosted, turn your air conditioner back on and run it normally. It should work properly now but watch it closely for signs of freezing up again. If you notice ice forming again, turn it back off and call a repair technician.

How to keep your air conditioner from freezing up

Of course, the best way to fix a frozen air conditioner is to prevent it from happening in the first place. Here’s how to keep it from happening:

  • Change your air filters regularly. This means every month or possibly even more often if you have pets or a lot of people in your home. Use your judgment or follow the advice of your AC repair professional.

  • Get a Preventative Maintenance Plan in place. This includes having an inspection and cleaning done by an HVAC specialist in the spring before the summer heat arrives.

  • Have an AC repair professional evaluate your air ducts for proper flow and clean them if needed.


Proper airflow is essential to cool your home. If the air isn’t moving through your system the way it should, there’s a good chance your air conditioner will freeze up. Properly maintaining your system and acting quickly when it isn’t working properly will go a long way in keeping your air conditioner blowing cold air for many years to come.

If you live in Baker, Crestview, and Niceville, Florida and need fast, friendly, and cost-effective repairs and maintenance call AC by DC LLC today or send us a message online. You can count on us to get your system up and running and have you cooling ASAP. But don’t take our word for it, listen to what your neighbors are saying!