Is your AC freezing up? It can be surprising to see a chunk of ice sitting on your AC unit, especially in the middle of summer. But sometimes, your AC can get frozen, even if you can’t see the ice on the exterior of the unit.
You may think an air conditioning unit cannot freeze in the summertime, but this happens frequently during the hottest days of the year.
If you fear you’re experiencing a frozen air conditioner, continue reading to find out the causes of an AC freeze-up, how to fix a frozen unit, and how to prevent it from happening again.
What Causes an Air Conditioner to Freeze Up?
To understand why an AC unit is freezing up, you first need to understand the basics of how central air conditioning systems work.
It all starts with your evaporator coils.
This key air conditioning component is full of extremely cold refrigerant—a liquid chemical that helps keep things cool. When the coils are activated:
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Warm air blows across the coils
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The air cools down
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The cool air goes into your home
The warm air also keeps the coils at a warm enough temperature that they do not freeze.
Then, the indoor coil:
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Removes heat from the inside air
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Transfers it using the refrigerant to the coil
The coil pushes the heat to the outside, which is why if you ever put your hand over the fan running on your unit, the air feels noticeably hot. However, if the air conditioner malfunctions, the whole system gets disrupted.
If something inhibits the warm air from blowing over the coils, the evaporator coil and the refrigerant cool too much, causing the temperature to fall below freezing and ice over. Additionally, if the refrigerant pressure is wrong inside the coils, your system’s coils can become too cold and freeze.
4 Possible Causes of an Air Conditioner Freeze-Up
Here are the most common reasons why your AC is freezing up.
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Low Refrigerant
As mentioned, refringent is a liquid chemical that cools the air. A low refrigerant level usually indicates a leak somewhere in the system. If the refrigerant is leaking, ice can start to coat various parts of your unit, leading to a complete freeze—especially when excess condensation is present.
Signs of low refrigerant levels include a hissing sound coming from your unit, a lack of cool air in your home, and, of course, ice forming on your AC.
Leaking refrigerant can cause health consequences—it is a chemical, after all—so it’s best to call a professional HVAC technician at 866-399-2885 for a thorough inspection of your system.
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Poor Airflow
Proper airflow is crucial in ensuring the proper function of all parts of your cooling system. An AC freezing up because of a lack of airflow can happen in two ways.
The first occurs when warm air isn’t reaching the evaporator coil, resulting in the coil getting colder and colder until it freezes. The second is that cold air doesn’t come into your home, leaving the air in place and allowing it to freeze.
Airflow problems can occur if the unit is damaged, there are clogs in any of the lines within the unit, the fan is not spinning, or the air filters are dirty or blocked. Depending on what is causing the blockage to the airflow, you may be able to fix this quickly.
If the signs aren’t obvious, it’s best to schedule an appointment to have your unit professionally inspected.
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Dirty Evaporator Coil
We’ve talked a lot about the evaporator coil and its importance in the air conditioning process, but did you know it can get dirty? As air is brought in to be cooled, other particles, like dust and dirt, come with it.
While an air filter helps prevent most of it from entering the system, some contaminants will move through, causing a layer of grime to cover the coil. This buildup makes the coil work harder and harder because of restricted airflow, and grime can start to freeze on it.
Scheduling regular maintenance appointments will help prevent your evaporator coil from getting dirty and your AC unit freezing up.
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Clogged Condensate Drain Line
The condensate drain line helps remove excess water that accumulates during the cooling process. If the line gets clogged, the water can’t leave and will build up. Eventually, the water will freeze due to the evaporator coil.
What to Do When Your AC Unit Freezes Up
If you believe you are experiencing a frozen air conditioner, there are some simple steps you can take to troubleshoot the situation. Hopefully, these steps can get things back up and running again.
If these steps don’t help, call 866-399-2885. At ARS/Rescue Rooter, we offer emergency services for those especially hot days—ACs always seem to break down during the warmest times of the year.
Step 1: Thaw
Make every effort to avoid using the AC while the evaporator coils are frozen. Running the AC with frozen coils strains the AC compressor. Go to your electrical breaker and turn off the power to your AC unit.
Taking this step will keep the system from freezing up even more and begin to let the ice thaw. The AC compressor is the most expensive component in your air conditioning unit. The strain could damage this incredibly valuable part and set you up for a costly air conditioning repair service call.
Even if it’s blistering hot outside, the ice could take a whole day to melt completely. Don’t be tempted to break the ice with a heavy object or sharp tool. This easily damages components so much that you’ll need to replace multiple parts, which can add up financially, or worse, you’ll be forced to replace the system altogether.
Step 2: Dry
Once the ice has melted, you need to dry the evaporator coils. You can use paper towels or let the parts dry in direct sunlight.
Restore the power to your system and turn the blower on. Run inside and set your thermostat to only run the blower or fan, depending on the model of the thermostat you have, to circulate air around and through the coils to dry them quickly. Once the coils are dry, your system should resume operating normally.
Now that you know what to do if you ever encounter a frozen air conditioner, let’s talk about how you can keep this from happening.
How Do I Stop My AC Unit from Freezing Up?
It’s important to recognize that this is preventable. Whether you have a York, Carrier, or Lennox unit, take these measures to keep your HVAC system from freezing.
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Change Your Air Filter
The leading cause of a frozen HVAC system is a dirty air filter. The air filter cleans the air circulated into your home. As your AC system runs throughout the summer, the filter catches dirt, pollen, dust, and other allergens, which can restrict airflow and lead the HVAC coils to freeze.
Typically, we recommend checking your filter monthly, though you should change it as needed. For most folks, this is every one to three months.
Filter changes vary based on factors such as:
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The type of filter you have
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If you have children or pets in the home
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If you live in a high-pollen count area
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Whether a smoker lives in the home
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If someone with asthma, allergies, COPD, or congestive heart conditions lives in the home
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Schedule Regular Maintenance
It’s good practice to have an annual air conditioning maintenance service call. The professional HVAC technicians at ARS/Rescue Rooter ensure all of the following are checked and cleared for your system to run properly for the summer ahead:
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Inspect coolant levels and pressure to ensure your system runs at peak efficiency.
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Calibrate thermostat(s) and check proper cycle and temperature to improve comfort and control.
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Inspect and tighten wiring, contacts, capacitors, and relays to avoid expensive repairs.
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Ensure the evaporator coil is clean.
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Ensure the condensate drain is clear.
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Inspect and clean the condenser.
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Inspect the outdoor disconnect switch.
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Inspect the condenser fan motor and blades; lubricate if needed.
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Check compressor amps at startup.
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Carry out additional safety and efficiency checks.
It’s also a good safety practice to avoid handling coolant chemicals since they can be toxic. Leave it to our technicians and keep yourself away from handling them if possible.
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Have an HVAC Airflow Inspection
Obstructed airflow can keep the coils from properly cooling and lead to a frozen AC unit. Similar to a clogged filter, blocked vent returns and registers prevent adequate airflow to and from the system. This causes your system to work harder without a way to release the cooled or heated air.
Another good practice is to walk around your home and check that indoor air vents and registers are clear of any obstructions. If you’re experiencing weak airflow through your vents, your ductwork may be to blame.
In some cases, the ductwork is installed well but is the wrong size or capacity for your house. Or there’s a duct leak, or a section of ductwork has collapsed somewhere within your walls.
Another potential cause of your AC freezing up is poor efficiency within your home. Proper ventilation throughout the structure allows the cooling system to operate more efficiently. Schedule an inspection with a professional HVAC technician for insights into which of these issues may be impacting performance.
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Clean Evaporator Coils
The condensate lines drain excess moisture from your HVAC system. If there’s a clog in the line, the water becomes stuck, and the excess water freezes. The frozen water in your lines could leave you with frozen HVAC coils, causing your system to struggle or not work at all.
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Check the Forecast
Are summer temperatures expected to drop at night? A good rule to remember is that when the outdoor air temperatures dip, you should turn your air conditioner off. Icing can occur if you run your unit on cooler nights.
Installing a special ambient temperature control can help prevent your unit from running in cooler weather because your thermostat shouldn’t remain at the same level all the time.
A Frozen AC Is Avoidable
While finding a frozen AC system can be frustrating for homeowners, this doesn’t always mean it’s time to show off your DIY skills. Depending on the reason for the freezing, you can cause more harm than good, possibly voiding your warranty, and need a new AC unit installed.
If you have no experience working on an AC unit, it’s best to leave it in the hands of professionals. It’s also important to note that the problems that cause freezing are preventable. Don’t neglect regular maintenance and tune-ups on your air conditioner each year.
Hiring a professional HVAC service team, like ARS/Rescue Rooter, or taking advantage of maintenance service plans, can help keep your system running strong all year long and save you money.
Find our nearest location to schedule service online or over the phone at 866-399-2885. We’re standing by for any emergency air conditioning service—including an AC freezing up.
Frequently Asked Questions
What happens if I ignore a frozen central air conditioning system with low refrigerant levels?
If you let your central AC system freeze while its refrigerant levels are low, it can lead to numerous problems. Without the proper amount of refrigerant, absorbing and releasing heat becomes much more difficult, hurting the system's ability to cool your home.
This also puts additional strain on critical components, increasing the risk of damage, including compressor failure. The ongoing freeze-thaw cycles can impair the system, leading to costly repairs or even a full replacement. A loss of efficiency may also result in higher utility bills.
What happens if I don’t address airflow issues in my frozen central air conditioning system?
Airflow problems caused by a frozen air conditioner can make your home uncomfortable. Without proper airflow, your home won’t be cooled evenly, making some areas warmer than you might like. This can also strain your system, resulting in breakdowns and costly repairs or replacements.
You may also experience higher humidity levels, which can cause mold and mildew growth and indoor air quality concerns that can harm your family’s health.
What if I don’t have recurring freezing issues with my air conditioner resolved?
If you have recurring freezing issues with your air conditioning system and fail to address the underlying reasons, you could be in trouble. Constant freezing is often a sign of problems such as poor maintenance or malfunctioning components, which can lead to lower efficiency, higher energy bills, and even damage to your compressor.
In the meantime, inconsistent cooling can make your home less comfortable and put extra stress on your AC unit’s components. If you do nothing while experiencing these issues, you could be facing expensive repairs or even needing your entire system replaced.
How do I unfreeze my air conditioner fast?
The fastest way to unfreeze your air conditioner is to turn off your thermostat. This stops your AC from blowing cold air and prevents the ice from spreading further. Next, turn the fan on so warm air can circulate through the unit, which speeds up the warm-up process.
You can try using a hair dryer to help melt the ice even more. Don’t turn the temperature all the way up, though, as that could damage the inner workings of the AC unit. Again, consulting with a professional might be the best option in this case.
How long does it take to thaw a frozen air conditioner?
A frozen air conditioner can take anywhere from an hour to a full day to thaw completely, depending on the severity of the ice spread and the size of your unit.
Can I fix a frozen AC myself?
Most of the time, you can’t fix a frozen AC yourself. It’s best to schedule an appointment with a professional, as doing it yourself could unintentionally cause more problems.
You can thaw out your unit and check for obvious problems, such as clogged drain lines or blocked air filters.
Will my AC unit work after it thaws out?
Whether your AC unit will work after it thaws out will depend on why it froze in the first place. If it’s because of dirty air filters or clogged drain lines, then yes, it will technically work—just not well.
Other more severe reasons for a frozen AC unit may cause lasting damage to the unit. Water leaks can also result in costly damage to your living space.
How can you tell if your AC is frozen?
Beyond the obvious sign of ice, you can tell your AC is frozen if you hear a hissing noise or notice a decline in performance.
