Why Is Your Window AC Freezing Up: Causes And DIY Fixes

Window AC Freezing Up

A Window AC is supposed to cool the air around you. In the high temperatures of summer, its job is to cool you with a gentle touch and comfort so that you never run into stressful conditions in your own home or office.

From this, we can establish that heat is the ultimate enemy. In fact, any extreme temperatures can be hindering our bodies and our minds.

So it’s safe to say, that much like heat, freezing ice is not exactly welcome. Much more so when you have frozen ice gathering inside your Window Air Conditioner. 

This article mainly aims to answer this question: So, what do you do if your Window AC Unit freezes up? Because, sure, you signed up for lower and cooler temperatures when you bought an AC, but you didn’t sign up for literal ice to build up inside your home and AC unit. 

In fact, if your find frozen ice built up inside your AC unit, it’s probably not a good sign. If you continue running your AC unit despite the ice, it can cause temporary or permanent damage to your AC.

This is why it is important that you tackle the problem as soon as it arises. In the following lines, we’ll explore the possible causes that lead up to ice formation in a Window AC, as well as discuss ways to Unfreeze it back to normal. 

How does an AC freeze up?

First, before we delve into the causes of an icy window AC unit, let’s figure out what parts of an AC are actually affected to bring about a frozen over.

Typically, the cooling process of an AC unit includes the warm air from the room being absorbed into the unit and being passed over the cold fins of the evaporator, where it is cooled.

The heat from the air, on the other hand, is transferred to the refrigerant inside the evaporator coils, which sends it all outside.

As the evaporator cools the air, moisture forms on its surface, which is collected in the drain pan, and disposed of outside. However, if the unit faces and problems with the airflow or the flow of refrigerant, it can lead to freezing up of the moisture. Consequently, ice starts forming all over the Evaporator. 

Reasons for Freezing up of Window Air Conditioner

Clogged Air Filter

One of the most important reasons leading up to the freezing up of your Window AC unit is that it is getting inadequate airflow from the outside. What this means is that your unit is not receiving enough air from the room to cool.

This could be because of various blockages in the unit. Generally, one of the first places to look for at a time like this would be the air filters. 

The Air Filters are one of the first components to make immediate contact with air from the room. The filters are designed to catch dust and debris and prevent it from traveling further inside the Air Conditioner.

In this process, it is possible that your air filter might have clogged up due to too much dust and dirt. This can happen easily especially if you haven’t cleaned your air filter in a while. 

Following this, the air usually flows through fins before the evaporator and after the condenser, as well as the refrigerant in the coils. The dust and debris, as discussed above, might be causing blockages in these areas too. 

Thus, it is advised that you thoroughly clean these components to help unfreeze the AC. The fins have very minute spaces between them, and they must be handled carefully with sensitive fin combs so as to not cause further damage. 

Broken Blower fan

Another reason why your Window AC unit might get frozen up is that the Blower Fan is broken or damaged. Again, this messes with the airflow rate inside the unit. 

The blades of your blower fan circulate the air inside the unit and make sure the flow is good so that it reaches the refrigerant coils. However, without proper airflow because of a broken Blower fan, you might run into an iced-up Window AC. 

Similarly, the same scenario might also take place if your fan setting is simply too low- that means that your fan is drawing in warm air at a slow rate, and it’s not fast enough to replace the air over the coils and prevent the moisture from freezing. 

AC Is Running At Very Low Temperature

If your refrigerant coils start freezing up, it could also be because you’re running your AC at a too low temperature, especially when the weather is cool. This will push cold outside air into the unit, which is pointless against the evaporator.

In turn, this will cause the moisture on the coils to start freezing up. As a general rule, if the temperature outdoors is less than 60 degrees Fahrenheit, we advise that you raise the temperature of your AC.

Damaged Drain system

Something could also be wrong with the draining system if your evaporator coils start to feel icy. The drain pan below the evaporator collects all the moisture that drips down from the refrigerant.

However, if the drain pan is damaged, and it can’t efficiently gather the moisture fast enough- then it may start freezing up on the evaporator. 

Leak in the Refrigerant

If you find that your Window AC unit is freezing up, this could also simply be because of the refrigerant itself. If the refrigerant levels is low because of a leak, this can seriously mess with the unit. 

First of all, a refrigerant leak itself is a big red flag. The refrigerant gas is supposed to stay inside the coils for all the working life of the unit. If you face this problem, you might want to call in a technician to take a look at your AC as this is beyond your jurisdiction. 

Too low refrigerant gas slows down the airflow, and also considerably lowers the temperature of the evaporator. As a consequence, this freezes the moisture before it has the chance to drain away. 

Your Window AC is too big

If your AC unit is larger than required for the room, you have a problem in your hands. These kinds of ACs cool and circulate the air very quickly without removing any humidity at all, and then automatically turn off. This is called short cycling.

This also means that, as the AC absorbs air again, the outside air is already cool. As a result, this can cause the moisture to freeze. So you must check the size of your ac unit. You can also call an HVAC technician and they’ll tell you if your ac unit is too big or not.

How to Unfreeze your Window AC Unit?

Window AC units typically have a life of around 8-10 years, which can be more or less depending on the external and internal conditions of the AC. When you’re handling such a big and complicated unit in your home, it’s not a surprise that you’re running into various problems. 

In fact, most of these issues are probably maintenance-related. If you treat your AC with care and keep it clean regularly, your Window AC will run smoothly for the larger part of its life.

For instance, if you use your AC Unit twice during the summer and fall season, make sure that your AC gets a thorough head-to-toe wash through at least twice a year. 

Step 1: Change Or Clean Your Air Filter

One of the first things to look out for is the Air Filter, which is located behind the grill of the AC. As discussed, the air filter traps dust and debris, reduces airflow, and leads to the formation of ice on the evaporator coils.

To fix this, it’s time to gently take out the filter and wash it thoroughly, or replace it with a new one. 

Step 2: Check And Replace Your Blower Fan

To deal with the blower fan, you’ll have to check for sure that the component is broken. Additionally, you have to also make sure that the motor attached to the fan is in working condition.

If you find that the fan is broken or damaged, you’ll have to replace it. If the motor can be easily turned on by the hand but it is lacking in performance, it needs to be replaced too. But If the motor isn’t turning in at all, call in a technician to take a look.

Similarly, with other defective parts, like the drainpipe, the easiest solution is to replace them with new ones.

Step 3: Check And Tweak Your Thermostat

If you simply find that it is extremely low temperatures making your AC freeze, simply crack up the thermostat. But it’s also possible that your thermostat itself might be wonky.

In such cases, check for the thermostat’s sensing bulb (this detects the temperature in the room and adjusts the ACs temperature accordingly). If you find any damages to the sensing bulb, replace the part. 


The was our take on the Frozen Window AC Unit problem. Primarily, though, we advise you to keep up your AC maintenance regularly and frequently to avoid this problem altogether for a long time. We hope this article might have helped you in some ways.

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