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In the sweltering heat of a St. Louis summer, few things are as distressing as discovering your air conditioner has frozen up. When your air conditioner freezes up, it’s not just an inconvenience — it’s a critical issue that needs immediate attention. This common problem may seem out of place, particularly when cooling is most needed, yet it’s a frequent occurrence that can disrupt your HVAC system’s functionality and, if not addressed promptly, can result in costly repairs.

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Here, we’ll explore the key causes behind a frozen air conditioner and provide a step-by-step guide on what to do when your AC is frozen up to prevent future issues.

Through these insights, you can ensure your air conditioning runs smoothly and efficiently, keeping your indoor environment comfortable and consistent all year round. Whether you reside on the Missouri or Illinois side of the river, Indoor Comfort Team is the trusted name you can rely on for all your HVAC needs.

So, grab a cool drink, sit back, and let’s dive into the steps you can take when faced with a frozen AC unit.


How will I know if my AC is frozen?


Other than visible ice on any part of your HVAC unit, the next most obvious sign of a frozen AC unit is a lack of cool air. If you put your hand in front of your supply vents and you sense warm air coming out, you probably have ice somewhere in the system.

You may also notice a hissing sound coming from the unit. If that’s the case, take steps immediately to prevent further damage. Your wallet will thank you later.


Understanding Why AC Units Freeze:

Firstly, it’s essential to grasp why an AC might freeze up, as understanding the root causes can help prevent future occurrences.

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1)   Poor Airflow

If you’re wondering what caused your AC to freeze, the most common culprit behind a frozen AC is poor airflow.

Restricted airflow can stem from several issues, but primarily, clogged air filters and dirty evaporator coils play significant roles. Air filters may not catch all dust and debris, allowing some to accumulate on the coils. This buildup restricts air movement over the coils, causing temperatures to drop and ice to form. Regularly cleaning these coils and frequently changing air filters are essential steps in maintaining efficient airflow and preventing your AC from freezing up.



2)   Clogged Condensate Drains

Another common cause for a frozen AC unit is a clogged condensate drain. If you have leaking water, this points to a drainage issue. You will want to double-check your pipes to help you rule out this much more basic and easy-to-fix problem.

If you find a clogged condensate line and don’t feel confident taking care of it yourself, call on the professionals at Indoor Comfort Team 24 hours a day at (314)230-9542.



3)   Damaged Blower Fan

The blower fan pushes warm air to the coils in your unit. If the AC blower fan malfunctions and isn’t blowing enough air, or any air at all, the evaporator coil will freeze, and the air conditioner will stop working.

If you notice damage to the blower fan, one of our technicians would be happy to get it repaired or replaced for you. Give us a call anytime at (314)230-9542.

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4)   Low Refrigerant Levels

Another major factor contributing to an AC freeze-up is low refrigerant levels. When the refrigerant level is inadequate, it leads to a decrease in pressure within the system. This drop in pressure results in lower temperatures, which can cause the coils to become extremely cold. Under these conditions, when the air conditioner continues to remove moisture from the air, the moisture can freeze directly on the coils. This issue often indicates a leak somewhere in the system, which could be through small pinholes, broken lines, or corroded fittings. Identifying and repairing these leaks is crucial for restoring proper function and preventing future freezes.

If you suspect an issue with your refrigerant levels, call in the HVAC experts of Indoor Comfort Team, and we’ll have you fixed up in no time – (314)230-9542.



5)   Check for Dirty Vents

Dirty vents that are in need of cleaning can be another possible cause for a frozen AC unit. This is another easily fixed issue, but it may be a sign of a serious maintenance problem.

Check all your vents to ensure they are clean and haven’t been blocked. Also, remember to check for dirty vent grills near doors, windows, and other openings to ensure haven’t been blocked.


6)   Incorrect Thermostat Settings

Setting your thermostat too low can also contribute to your AC unit freezing up. It’s recommended to keep the thermostat set above 67°F. Lower indoor temperatures can reduce the refrigerant pressure too much, mimicking the effects of colder outdoor conditions, which can lead to ice formation on the coils.

To rectify the situation, it’s advisable to allow your AC to thaw and then adjust the thermostat to a more moderate temperature, ensuring it does not drop too low. This approach helps maintain both efficiency and prevents freezing, creating a balance between comfort and system performance.

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Step by Step: What To Do If Your AC Freezes Up




When faced with a frozen AC unit, acting swiftly and safely is crucial. Follow these steps to restore your system:


●      Turn Off the AC

Immediately switch off the unit to prevent further ice build-up and potential damage to the compressor. This will prevent you from wasting too much electricity.



●      Thaw the Unit

Allow the ice to melt naturally by turning on just the fan modem which circulates air without cooling it. As the ice melts, you might want to consider opening up the ducts and using a wet-dry shop vac to vacuum away the water.



●      Inspect and Change the Air Filter

Regular maintenance of your air conditioner’s air filters is crucial for preventing freeze-ups. According to most manufacturers’ recommendations, you should inspect your filters routinely and replace them as needed, typically every 60 to 90 days. In environments with high levels of pollutants or pollen, you may need to check and replace the filters more frequently.

Clogged or dirty filters can block the flow of warm air into the AC unit, significantly reducing airflow and potentially leading to freezing issues. If a simple filter change doesn’t resolve the freezing, this might indicate a more serious problem, such as a refrigerant leak, which would require the expertise of a certified HVAC technician. Regularly replacing your air filters is one of the easiest and remains free from common operational issues like freezing.



●      Clean the Coils and Check Vents

Ensure the evaporator coils are clean and all vents are unobstructed. Also make sure to find the condensate drain and check that it is also not clogged.

Keeping the evaporator coils clean is crucial as they can become obstructed with dust, pet dander, hair, or even moldy residues. Such build-ups insulate the coils, preventing effective heat transfer from the air through the fins into the refrigerant. This insulation can cause the coils to drop to freezing temperatures, leading to moisture condensing on them and eventually icing up. To prevent this, coils should be cleaned regularly. If you find the coils frozen, allow the unit to thaw completely before attempting to clean them. This can be a detailed process, but thorough cleaning is key to maintaining your AC’s efficiency and preventing freeze-ups.

Never worry about any of this again with our maintenance agreement. With our VIP Club Maintenance Plan, our team will come out twice yearly for maintenance for as low as $20 a month. Visit https://www.indoorcomfortteam.com/services/maintenance-agreements/ or give us a call at (314)320-9542 to learn more.



●      Restart the AC

Once you have ensured that everything is fully thawed and the evaporator coils are thoroughly cleaned, it’s time to restart your air conditioner. However, do so only when the ice has melted, and the pan containing the condensate has drained completely.

When you turn the AC back on, it’s important to closely monitor its performance to ensure that the issue of freezing has been resolved effectively. Watch for consistent airflow and listen for any unusual noises that might indicate lingering problems.

Don’t forget to check that the temperature of the air being emitted is gradually returning to the desired setting. This is important as it confirms that the maintenance tasks have been successful and that the system is running smoothly without further complications. Continuing to observe the unit’s performance over the next few hours or even days will help you ascertain that the issue has been fully rectified and will not recur promptly.



●      Call for Professional Help

If your air conditioning system doesn’t respond to these basic troubleshooting steps, such as turning it off and allowing it to thaw, this could signal more serious issues, like a refrigerant leak or severe component damage. Ice build-up on the coils, lines, or compressor is often a clear indicator of underlying problems that require professional intervention. Due to potentially low refrigerant levels, the problem can worsen over time. Call the Indoor Comfort Team 24 hours a day at (314)230-9542.



Preventive Measures to Keep Your AC Running Smoothly

Preventing an AC freeze is easier and often more cost-effective than dealing with it after the fact.  That said, by learning what to do when your AC is frozen up, you can avoid significant disruptions.



Here are a few practical tips to maintain optimal operation.


●      Regular Maintenance:

Schedule annual inspections with your HVAC technician to keep your system in peak condition. Indoor Comfort Team offers our VIP Club Plan for affordable twice-yearly maintenance. Visit  https://www.indoorcomfortteam.com/services/maintenance-agreements/ or give us a call at (314)230-9542 to learn more or to sign up.


●      Proper Settings:

Avoid setting your thermostat too low; aim for a comfortable but not overly cold temperature.


●      Routine Cleaning:

Regularly clean or replace air filters and ensure the area around your AC unit is free from debris.



●      Check Ductwork:

Inspect the ductwork for leaks or blockages that could impact airflow. Leaky ducts can cause loss of warm air needed to keep the coils from freezing, and blockages can restrict airflow, both of which can contribute to a freeze-up. If you suspect a ductwork issue, our technicians are highly trained to diagnose and repair any issues that may arise. Give us a call anytime at (314)230-9542.


●      Monitor Refrigerant Levels:

Ensure that your AC system has the correct amount of refrigerant. Low refrigerant levels are a common cause of freezing because they reduce the system’s pressure, leading to a lower temperature that can freeze the condensation on the coils.


●      Optimize Air Circulation:

Ensure that the vents in your home are not blocked by furniture or curtains, and consider using fans to improve circulation. Better air circulation helps maintain an even temperature throughout your home and reduces the burden on your AC System.



By following these tips, you can significantly reduce the risk of your AC unit freezing up and ensure it runs efficiently throughout its lifespan. Remember, understanding what to do when your AC is frozen up and performing regular checks and maintenance are invaluable in keeping your system running smoothly.

As we wrap up our guide on dealing with a frozen AC unit, remember that the Indoor Comfort Team is here to support you every step of the way. With our decades of experience and unwavering commitment to customer satisfaction, we’re dedicated to keeping your home cool and comfortable, no matter the season.

By following the steps outlined in this blog, you can not only thaw out your air conditioner but also prevent future freezing issues through regular maintenance and proper care. However, if you ever need professional assistance, don’t hesitate to contact our team of expert technicians at (314)230-9542. We’ll quickly diagnose the problem and implement effective solutions to get your AC running smoothly again.

Thank you for trusting the Indoor Comfort Team as your HVAC partner in St. Louis and beyond. Stay cool, stay comfortable, and remember that we’re always here to ensure your indoor comfort.

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Contact us today!

Indoor Comfort Team has been a trusted name in the greater St. Louis area since 1979. Whether you live on the Missouri side of the river or in Illinois, our skilled and licensed HVAC technicians are ready to deliver the services you need.

We provide complete heating and cooling installation and repair as well as water heater and indoor air quality services.

Need a repair today? Call (314) 230-9542 or (618) 688-0707.

Whether you need repair, maintenance, or new installation of your furnace or air conditioner, contact us today to let us get our comfort specialists right to work on your home or business.

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