Unfreezing the Chill: How to Fix a Frozen or Stuck AC Unit

A frozen AC system in the middle of summer can be tremendously annoying! If you have noticed that cool air is no longer being pushed into your house or hear hissing from the unit, it may be frozen. There are several ways this can happen as well as some ways to prevent it.

Most times your AC is freezing up because of a dirty art filter or evaporator coils. Refrigerant leaks or bad compressors can happen over time and are a bit more serious. It could also be blocked systems in your vents or a clogged drain pipe.

Being able to identify these various causes can help you fix the system on your own to tell you when you need to call a professional.

Having a general knowledge of the signs of a frozen AC is also great information for homeowners to know! Follow along to get a sense of the most important information regarding your AC system.

How To Tell If Your Air Conditioner Unit Is Frozen?

The most obvious sign that your air conditioner unit is frozen is the lack of cool air flowing into your home. If you suspect this, hold your hand by an AC vent while the system is on. If you feel slightly warm air you know the system is frozen. 

Once you have noticed this, you need to investigate your outdoor compressor unit. You may hear a light hissing sound coming from the unit and see ice built up around the HVAC unit. These are tall tell signs that the problem with your air conditioner is that it is frozen! If you see these signs, be sure to turn off your AC system immediately to avoid further damage. 

What Causes An Air Conditioner To Freeze Up?

As it is with all machines, certain parts break down over time. If one part gets broken or clogged, that can set off a chain reaction that causes the air conditioner to freeze.

Regular maintenance on your unit can help prevent these from becoming large problems. But here are a few explanations on why the freeze could be happening.

1. Dirty Air Filter 

Dirty or clogged air filters are a very common reason for your AC freezing up! These filters impact the airflow of the air conditioner unit and can keep the unit from turning off or help trap ice if the system malfunctions. Luckily, dirty air filters are easy to fix and prevent!

To prevent this you will want to change your air filters at least once every three months. If you use your AC a lot, once a month is even better to keep this part clean! Otherwise, it could get clogged and collect ice, leading to the system freezing more quickly. It also helps keep your air quality clean.

2. Dirty Evaporator Coils

Dirty evaporator coils are a secondary effect of a dirty air filter. Dust and debris can accumulate in refrigerant coils and are allowed to cling to them due to the present moisture.

This combination leads to lots of problems, and ice can quickly take over and block up the overall system and prevent it from working. 

The easiest way to prevent this is the same as with air filters! Keeping this part clean will prevent the dust from reaching the evaporator coils. Once you thaw the AC system this ice will go away, but if there is a lot of dirt on them you will need a professional to disassemble the parts and clean them out.

3. Refrigerant Leak

An AC system with low refrigerant levels can lead to ice building up all over your system. Which can lead to the system not working properly from the low refrigerant as well as the blockage of the built-up ice.

You mustn’t try to add more refrigerant. Refrigerant does not evaporate in the closed AC system, so if there is not enough it can only mean there is a leak. This leak could be anywhere, from the refrigerant lines to the evaporator coils. If this is the problem you will need to call a professional.

4. Incorrect Thermostat & Fan Settings

Keeping your set temperature and fan low can affect the functions of your AC system. Especially if your summers are very hot, you need to run the fan on high to keep the temperature inside cool. Low fan speeds can strain the unit, and combined with a low temperature this can lead to ice build-up.

A DIY solution is to increase your fan speed or increase the temperature to give extra warmth and airflow to the system. However, the best way to prevent this is to avoid running your AC for long periods at very low temperatures. This is to be sure you do not overwork the system and keep it within its ideal operating range.

5. Bad Compressor 

Compressors are the central function of any air conditioning system. A worn-out compressor will not effectively pump refrigerant through the system. Which can lead to condensation on the coils that eventually turns to ice.

Unfortunately, you cannot fix a bad compressor, and it is recommended that you replace it on a priority basis. This is an instance where you certainly need to call in a professional. A good way to prevent this is simply regular HVAC maintenance.

6. Clogged Drain System

The drain system is very important to an AC unit, as it is where the leftover moister taken from the air is put outside the system. If there is a clog in this drain line, the cool air mixed with the extra water could freeze and back up the rest of the system.

Turning off your AC system and letting the ice melt may help if the clog is easy to reach in the drain pipe. But if it isn’t a professional can help. The best way to prevent these clogs is through regular maintenance! 

7. Faulty Blower Fan Motor

If you have tried turning on your fan to melt off some of the ice on your AC unit and it does not seem to help, a broken fan may be the source of your problem!

Poor airflow leads to ice build-up, and if the fan is busted there is no help for the result of the system. A broken fan will need to be fixed by a professional, so there is no DIY solution you can do on your own.

8. Vent Blockage 

Airflow is a major component of ice build-up, and vent blockages could be a reason for it. If too many of your air grates are closed, airflow becomes reduced or gets backed up in the ducts. This then leads to less air being circulated over the coil where it gets too cold and the moisture condenses and freezes.

One solution you can try is to turn the thermostat to the Off position or only the Fan position and allow the coil to thaw. It is also helpful to open all of your home’s air grates to assist in this process. Ideally, this will release the block and the ice and allow the system to work on its own again.

What Should I Do If My AC Freezes Up?

Once you have realized that your air conditioner is frozen, you will need to try and thaw it out as soon as possible to avoid larger damages. You will need the unit to be thawed out before you can investigate bigger problems. Luckily it only takes a few easy steps!

Step 1. Turn the air conditioner completely off 

As soon as you notice the AC unit is frozen, immediately turn it off! Running the system while frozen can quickly damage all the functions. The compressor in particular is sensitive to this widespread damage and is the most expensive part to replace.

To prevent long-term damage or the need to buy a brand-new system, you need to turn the AC unit completely off.

The COOL or LOW setting is not enough, so be sure you shut it down completely to begin defrosting your system.

Step 2. Turn your thermostat fan on

Next, you will want to turn the HVAC fan to the ON setting. Be sure that the fan is set to ON and not AUTO to keep the air continuous. Your indoor thermostat should have the option for you to do this even with the air conditioner system completely off.

By doing this, you will force warm air to blow over the frozen system. Thereby melting off the ice on the frozen coils which simply speeds up the defrosting process. Once the system seems thawed out, you can turn the air conditioner on again and keep an eye out for more freezing. 

Step 3. Call a Professional 

If you have tried these two steps, watched your AC for a few days, and the problem returns it is time to call a local professional.

Unfortunately, changing the air filter is the only solution you can safely do on your own. So if the problem seems to be the coils or a broken fan, then you will certainly need to call some is qualified to assess your system.

Once you have tried everything you can, you will need someone with the right tools and understanding to work on the problem. Otherwise, you could risk damaging the unit more by trying to fix the larger problems on your own. 

Will My Air Conditioner Fix Itself? 

The air conditioner will not fix itself if you just leave it alone. Hopefully, these steps mentioned in the earlier section will be able to unfreeze your air conditioner and get it running again! However, if thawing the unit and changing the air filter does not fix the problem then you have bigger issues to deal with. 


There are a few measures you can take to help a frozen AC work on your own. But if none of the simple measures work it is best to call a professional to be sure the unit gets fixed soon.

Here is an extra tip for those who read through the article. Do not run your AC on cool nights, as it can cause the AC to freeze up!