Why Is My Air Conditioner Freezing?

There is nothing more frustrating then finding that your air conditioner isn’t working during a hot summer’s day. As I write this article it’s a few days before Memorial Day and it’s already starting to get hot here in Kansas City. For those of you who don’t know, it can get damn hot here in Kansas during the summer. I’m talking one-hundred plus degrees. If and when your air conditioner stops working it can be even more perplexing when you go out to check on your air conditioner only to find ice all over the machine.

To a lot of folks this just makes things more confusing. The air conditioner is obviously working… as there is ice all over the machine, but why isn’t that cold air moving to your home and why is the machine iced over? That folks is what we are going to tackle in this article. A frozen air conditioner is actually one of the most common questions that HVAC technicians receive and in most cases it can be resolved rather quickly and painlessly.

Ice Ice Baby

Frozen Air Conditioner
Frozen Air Conditioner

Yes, yes… I know. It’s a horrible song and it also shows my age. First thing is first, when it comes to ice on your air conditioner it doesn’t matter if it your traditional split system air conditioner, a ductless system, or even a window air conditioner. All of these different types of air conditioners work in the same way and they all be corrected in the same fashion. When your air conditioner does freeze you will notice frost, and maybe even chunks of ice, on the copper lines leading to your outdoor unit. You may also see that frost and ice transition over to your outside system as well. That being said, please also note that some slight frosting on the copper tubing that carries the refrigerant from the inside to the outside system is common and usual. It is when you notice heavy frosting or even ice accumulation that you need to start figuring out what is going wrong.


The first step in trying to troubleshoot your frozen air conditioner is turning the system off. If your air conditioner is still running while frozen then the ice and frost are only going to build up. If the ice is really bad you may even turn your thermostat to heat in an effort to speed up the thawing process. Some folks even take a battery powered hair dryer to thaw the ice. It is very important to note here that the ice should not be forcibly chipped off the copper lines and the air conditioner itself. Using tools could harm the lines and the air conditioner itself and end up costing you a whole lot more money then you need to. In some cases you can use water to slowly pour over the copper lines to help speed up melting. Do NOT pour water on the air conditioning unit itself as you could run into water damage and do not dump boiling hot water on the frozen lines. It is best to be patient and wait for the ice to melt.

While you are waiting for the ice to melt it is best to find the condensation drainage pipe and make sure that it isn’t blocked this is one of the main reasons why air conditioners freeze over. If the drainage pipe is blocked then you could have quite a bit of water with nowhere to go. This has happened to me in the past where my basement got slightly flooded due to the condensation line being clogged. Once I cleaned the pipe the water problem went away. When dealing with a window air conditioner it is best to tilt the unit slightly backwards so that the melting ice can drain safely out and away from the unit. Also, if you feel that water/ice had formed inside the ducts near your air conditioner you may consider opening these up and suctioning out water with a shop vacuum. (You would only need to review the central most ducts near your indoor air conditioner.)

Once the ice has melted and the water problem is gone you can try turning on your air conditioner again. In most cases you will find that the air conditioner will fire back on and began running without issues. In other instances, there could be a legitimate problem with your air conditioner and you may end up with iced lines again.

The Why

While your air conditioner may be running again after you cleared the ice there is most likely an underlying problem that will need to be addressed. There can be multiple causes as to why your air conditioner froze. I will try to cover them all here but if I missed something please do not hesitate to reach out to me. Let’s take a look at the most common reasons:

  • Air Filters – Hopefully this was the cause of your frozen air conditioner as this is the easiest and cheapest one to fix. I’ll admit that I am completely guilty of forgetting to change my air conditioner filter. There was a time I went nearly six months. Not changing this filter regularly will result in poor airflow due to all of the dirt and grime that gets stuck to the filter. This poor air flow will restrict the amount of hot air that your evaporator coils receive. Without the needed hot air your evaporator can freeze. By either cleaning or replacing your filter with a new one you may be able to prevent this from happening again and only be twenty or thirty dollars. Lately, I’ve taken to ordering my air filters online through Amazon as it’s much easier and I can even set on a reoccurring purchase that occurs every few months. When the new filter comes in the mail I know it’s time to swap them out.
  • Low Refrigerant – Each air conditioner has as specific amount of refrigerant that it is optimized for. If the system has a lower then needed amount of refrigerant the evaporator can end up running too cold. Please note that correcting this isn’t just as simple as adding new refrigerant. The air conditioning system is an endless closed cycle. In a perfect system refrigerant should not escape. If you are low on refrigerant that means that you have a leak somewhere in your system. This leak will need to be repaired before you put more refrigerant in. If not, then you are just throwing money down the drain and you will run into the same problem down the road. Depending on the type of air conditioner you have this could be a somewhat expensive repair to an extremely expensive one. The newer air conditioners (Since 2010) use a refrigerant known as R-410A. This isn’t too expensive, but it will still cost you to refill your entire system. Now, if your air conditioner is from before 2010 then chances are it is using a refrigerant known as HCFC R-22. This refrigerant is currently phased out and can be extremely expensive to refill your system.
  • Closed Vents – A lot of homeowners like to close vents in rooms they are not using. This is seen as a way to save money. This is all true, but if you close too many vents in your home then that cold air has nowhere to go and could end up freezing some of your lines or your air conditioner itself. Try opening up all of your vents when you turn on your air conditioner again. Watch to see if the problem occurs again. If it doesn’t, then try closing one or two vents, then watch your system again. Rinse and repeat until you determine what the ‘perfect’ number of closed vents is for your home.
  • Thermostat – There could also be a problem with your thermostat. If it is not reading the temperature in your home correctly then this could result in your air conditioner running all day and night. Not only is this going to cost you quite a bit on your power bill but it could also result in your air conditioner freezing. An overworked air conditioner could result in a freezing system.
  • Drainage – Your air conditioner’s primary job is to remove heat. It doesn’t necessarily create cold air but instead just removes the heat from the home. During the hot summer days the heat is removed as well as the humidity. When humidity is removed from the air water is formed. This is called condensation. I’m sure you’ve seen this before as this is where the water comes from that drains into the vent in your basement. If the drainage line is blocked then the water will either flood your basement or it will end up freezing as it’s stuck in the air conditioner. This frozen water will freeze in the drainage pipe and then work it’s way all the way back up to your evaporator coil. If you don’t see any water coming from your drainage pipe, especially in the hottest parts of the summer, then that very well may be your problem. This problem occurs in more humid climates like the south or like in Kansas where I live at.
  • Blower Motor / Fan Speed – For those of you who do not know, the cold air from your air conditioner comes from the fan or blower motor blowing air against the cold evaporator coils. (The evaporator coil is the inside part of your air conditioner that sits above your furnace.) The blowing air then becomes quite cold, but if the fan is not strong enough some of the coldness on the evaporator coils remains and could result in a frozen system. This can be solved by either increasing the speed of your blower motor or by installing a new more powerful blower motor. A new motor can get expensive, so I would try the other solutions here before you get to this step.
  • Ductwork – While this isn’t as common as the other possible reasons we mentioned above it is a possibility. If you have gone through your home and opened all of your closed vents and are still having an issue with freezing then it may be worth looking at the interior of your ducts. Do they look overtly dirty? Is there accumulation? It may make sense to have your ducts professionally cleaned. Along with looking at dirty ducts you may also inspect all of the routing of your ducts to ensure they are in working order. Ensure that they do not have any punctures, holes, or gaps. In most homes you can inspect vents via the attic. If you do end up going into the attic please take care and ensure that you are walking correctly through your attic. There is nothing worse then causing a whole other problem when trying to fix an existing one!
  • Window Unit Tilting – When you install a window air conditioner you need to ensure that the unit is slightly tilted. The tilt should be that indoor portion is slightly higher then the outdoor section. This will allow the water from condensation to drip out. If it is not tilted then you can end up with the same problem that we discussed earlier. The water will freeze and clog your drainage line. The good news is that troubleshooting a window air conditioner is much easier then a traditional split system air conditioner.


If after going through all of these possible reasons you are still having problems with an air conditioner that is accumulating frost or ice then it may be time to contact a professional. Remember, that a continuing freezing air conditioner can permanently damage your air conditioner. If the problem persists then it is worth contacting a local HVAC contractor to look over your system. Hopefully, the problem is not severe and your technician can resolve the issue, but in more extreme cases you may end up needing an entirely new air conditioner.


When I write articles I pull information from my gained experience but I also consult with various other websites to ensure that the information I am giving you is accurate and factual. That being said, here are the sources that I used to write this article. These are all great websites and I would especially like to point out my first source, ASM-Air.com. This site has a whole host of information, pictures, and videos on anything and everything air conditioning.