Why Do Air Conditioners Freeze Up

Why Do Air Conditioners Freeze Up? – Good Maintenance and Prevention

The modern-day air conditioning that we have now can be traced back to the 17th century where Cornelis Drebbel, a Dutch inventor, demonstrated the “Turning of Summer into Winter” by adding salt to the water. John Hadley and Benjamin Franklin later expounded this through an experiment about the principle of evaporation being applied to rapidly cool an object.

Without a doubt, the history of the air conditioner (AC) has been rich and we have the inventors to thank for it. But despite it being such a magnificent product of modern-day thinking, there are still some modern-day challenges that come along with it. Namely, it freezes up on us.

So, we ask, why do air conditioners freeze up? One might think that your AC freezing up is a good thing, and that it will produce stronger and cooler air. Unfortunately, it’s the complete opposite. The purpose of an AC is to cool down the room, but it is done through a delicate balance of pressure, airflow, and temperature. Once the room equilibrium is off balance, it can result in the AC freezing up. When it freezes up, it wouldn’t be able to do its job, and it will just cool itself down and not the room.

Could it be the air flowing around our homes? Or could it be brought by dirty pipes? These are the questions we seldom ask and we’ve got the answers for them.

Read on to know more!

How An AC Makes Cold Air?

Let’s first understand how an AC produces cold air before we get into why an AC freezes up. In basic principle, an AC works by drawing the heat energy out of the room and transferring the heat outdoors then replacing it with cold air. The law of equivalent exchange states that energy can’t be destroyed nor created, it can only appear in one form or another. That’s why hot air must be blown out, the hot air will not disappear, but instead it will disperse.

But how does it work exactly?

Here is a deep look on how the entire process works:

  1. Warm air is sucked to the grill of the AC, you can typically see these grills at the bottom half of the AC.
  2. The warm air then passes through a series of chiller pipes which is filled with coolant liquids. This same process can be found in the chiller section of a fridge. Once the warm air process through these pipes, the air is then cooled down and dehumidified. But this leaves the chiller pipes warm now.
  3. Since warm air has heated up those chiller pipes, they now needed to be cooldown so that they can be used again for cooling the air. To cool down those pipes, a strong fan inside the machines will cool down the coolant liquids within the chiller pipes.
  4. Now that the chiller pipes and the coolant is cool, it can be used again the cold down the hot air that is sucked in.
  5. But what about the hot air produced from cooling down the chiller pipes? Outside any buildings, you might have noticed some huge fans blowing hot air out. This is where all the hot air is blown out.

These same processes can be found in any coolant, whether it be a fridge or a car’s AC. But with the refrigerator, however, the heat is not blown out away, but is instead stored around or at the back of the fridge. That’s why when you touch a fridge on the outside, it feels hot.

Now that we understand the process thoroughly, let’s now begin to learn why the AC freezes up and how to fix it.

What causes an air conditioner to ice up?

Before going into details on how to avoid and fix it, let’s first figure out why do air conditioners freeze up in the first place.

One of the common reasons for what causes an air conditioner to ice up is a blocked airflow. Without a constant flow of air, the humidity entering the air conditioners ten to settle on the coils, causing it to freeze up. To allow great airflow through the system, you need to make sure that the air filters aren’t clogged or dirty. Dirty filters cause the system to clog up, restricting the airflow. Air conditioning filters are cheap so it would be best to either clean them up when you notice the air is not cold enough as it’s used to or buy another one for the unit.

The surrounding temperature of the area can also cause this issue. As we all know, summer nights tend to be a bit colder so this causes your system to go a bit crazy. Leaking refrigerants can also cause your air conditioner to freeze up. This happens when there’s a sudden drop in the pressure of the system flow, causing the fluid to get stuck up in some area, expanding and causing problems along the way. When this happens you would have 2 options left:

  1. Get some cash to spend on a fix that might be temporary
  2. Invest in a new unit

There are other reasons as to why do air conditioners freeze up but these are the most common culprits to take note of.

How do I keep my air conditioner from freezing up?

By now, you might be asking yourself, “How do I keep my air conditioner from freezing up?” Well, there are plenty of ways to avoid this scenario from happening:

  • Have your local technician do a checkup and cleanup of the air conditioning unit at least once every 6 months. This way, your technician can thoroughly clean out any dust accumulated on the coils and motor. They can also check for any refrigerant leaks early.
  • Clean or change the filter at least once every one to two months, depending on how dirty it gets. This is a crucial step as it is one of the most common reasons why do air conditioners freeze up. 
  • Make sure the air supply vents are not obstructed with anything. Allow proper airflow going to and from the unit.
  • Increase the fan speed so the cool air is blown out immediately. Do not give the coils a chance to ice up.
  • Check the drain weekly. Compare the amount of condensate accumulated. The fewer the volume, the higher chance your unit requires a technician visit.
  • Check the angles of the window units if they are on the right and leveled one. Too low or too high can affect how the refrigerant flows throughout the system. This might cause it to settle on lower points, causing a blockage.

How to unfreeze an air conditioner?

If this happens on a hot summer’s day and just in case a technician is not available right away, is there a way on how to unfreeze an air conditioner? Well, there is some first aid stuff you can try to do to help alleviate the situation. Similar to a frozen freezer where you need to thaw it out before even attempting to put anything inside it again, the same process applies to a frozen air conditioning unit.

To start the thawing process, you first need to turn off the air conditioning unit’s thermostat. Then check the air filters if they are still clear or in need of a cleanup. After that, leave the thermostat off and turn on the fan. Leaving the fan on for a couple of hours or more allows warm air to enter the system. This helps to thaw out the frozen coils. In some cases, leaving it this way for 24 hours can help fix the issue.

Say, after 24 hours, give the unit a test and set the thermostat to cool. If the air is somehow cooler than room temperature, you’ve fixed the issue. But if not, waiting for the technician to arrive is your only hope to fix this.


Air conditioners are a must-have now for locations that have a warm climate most of the time of the year. They keep us comfortable. At the right temperature, it can provide a really good night’s sleep and prevent our legs from cramping. And though freezing up is very common, it is a frustrating issue for some homeowners to experience. Doing some simple tuneups and regular maintenance should be enough for you to avoid such a stressful situation.

If the issue arises, you may try thawing the unit out as a form of first aid. But if the push comes to shove, let a professional handle it. We’re sure your local technicians can handle the job. They will give you the best advice on how to fix and even prevent the problem from happening again. Just be sure to mark your calendar and schedule a technician when it is needed. Why do air conditioners freeze up? Hopefully we’ve given you a sufficient answer.

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