AC Freezing Up: 5 Reasons and Troubleshooting Tips

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Air conditioners provide cool air to lower the temperature of the room, but a frozen AC unit would malfunction, causing the unit to blow warm air instead. When air conditioners freeze, they impede the flow of cool air into the room, and the AC unit is generally unusable.

In this article, we'll check the five most common reasons for an AC unit freezing up, and the five tips to prevent your air conditioner from freezing at all. As always, we recommend having your AC unit checked by one of our professional HVAC technician teams for the best possible aircon servicing!

Reason Description Solution
Dirty Air Filter Dust buildup causes the air filter to clog, resulting in poor air circulation around the unit. Dismantle your air filter from the AC unit, and scrub clean with some soap and water to remove the dust buildup.
Low Refrigerant Levels Refrigerant levels are too low for the AC unit to adequately function. This is most likely a sign of a refrigerant leak. Top up refrigerant levels on your next HVAC service, and have a technician check/fix any leaks with the refrigerant line.
Poor Airflow Blocked vents results in poor air circulation, as do problems with the fan motor, filters, etc. If the vent or filter is visibly blocked, use a brush to clear the debris buildup. If the problem is with the fan motor, take your unit to an HVAC technician to replace the broken fan motor.
Dirty Evaporator Coils Dust and debris form an insulation layer around the evaporator coil, causing condensate to freeze around the coil. Have your air conditioner undergo a general cleaning or chemical wash at least once every six months to prevent this problem.
Clogged Drain Lines Condensate gets trapped within the AC unit and freezes. If the clog is visible and easy to clean, you can use a long stick or wooden chopstick to clear the debris. Else, take your unit to an HVAC technician to fix the problem.

5 Reasons Your AC Unit is Freezing Up

Reason #1 Dirty Air Filter

The most common reason for an air conditioner freezing is a dirty air filter. When the filter accumulates dust and debris, it can block proper airflow going in and out of the air conditioning system. This causes an air conditioner to freeze up as the cooled air cannot escape properly, and the condensation around the unit freezes.

Reason #2 Low Refrigerant

The refrigerant is what cools the warm air that goes into the air conditioning unit. When the refrigerant levels are low, the evaporator and condenser coils freeze up as a result of cold air running through the inside of the air conditioner. This may be the cause of a frozen air conditioner, particularly if you have refrigerant leaks.

Reason #3 Poor Airflow

Poor air flow coming in and out of your air conditioner is another cause for a frozen AC unit. Poor air flow is an indication of a problem with the air filters, blower fan, or other internal parts of the AC unit. Cooled or heated air cannot properly pass through the AC system, causing the unit to freeze.

Reason #4 Dirty Evaporator Coil

If your AC unit has not been professionally cleaned in a long time, it may freeze up due to dirt, dust, and debris forming around the evaporator coil. This causes a layer of dust that acts like an insulator around the evaporator coil, which causes cold condensate to get trapped within the unit and freeze.

Reason #5 Clogged Condensate Drain Line

The drain line is responsible for keeping the humidity out of air conditioners as the water is directed to the condensate drip tray instead. If the drain line is clogged, it can trap the humidity within the AC unit, causing the air conditioner to freeze.

5 Tips to Prevent AC Freezing Up

Tip #1 Clean the Air Filter Regularly

Cleaning a clogged air filter is an easy fix. You can DIY the cleaning by removing the filter according to the manufacturer's instructions, and run the filter under soap and cold water to remove the dust buildup. Use a soft-bristled brush to gently scrub away at the particles trapped within the filter, and let the filter dry before placing it back into the AC unit.

Tip #2 Top Up Refrigerant Lines as Needed

Don't forget to top up your AC refrigerant coils the next time you have your unit serviced. The refrigerant is an essential component of your air conditioner that is responsible for cooling the air, so it is pertinent to ensure refrigerant levels are adequate.

If you suspect your unit may have a refrigerant leak, contact Luce Aircon to have one of our technicians diagnose and repair your unit, as well as clear any impending issues with your air conditioning system!

Tip #3 Air Conditioner Would Need Regular Maintenance

Air conditioners need a general cleaning and maintenance service at least once every six months to keep the units running smoothly. Consider scheduling an appointment with one of our experienced technicians, and we can take a look at the condition of your HVAC system.

We'll be able to fix issues before they damage your unit, and keep your unit in tip top shape so it will last longer to provide you cooler air. We can check every part from evaporator coils to fan motors to ensure each piece is working well without any issues!

Tip #4 Avoid Using Air Conditioner in Cold Weather

Using the air conditioner in cold, icy weather can also cause the unit to freeze up. The condensate from the air can freeze the evaporator coils, the condensate drip lines, and other internal parts of the air conditioner. Avoid using the air conditioner in freezing weather.

Tip #5 Ensure Vents are Clear

Check all the vents to avoid air conditioner malfunctions. Ensure that there is nothing blocking the air flow with the indoor vents, as well as the vents in the outdoor unit. Use a flashlight to check the vents from time to time. Clear dust from the vents using a long-bristled brush to wipe away any debris buildup.

The Big Freeze

It is not uncommon to see a frozen AC unit, but it does indicate an ongoing issue with your unit that needs to be addressed immediately. To keep your unit working well for decades to come, consider having it checked by one of our HVAC professionals on a scheduled basis as we can ensure the good condition of your unit. Aircon services will prevent problems in the future, and avoid the high costs of having to repair the damages to your air conditioner later on.

Check out our article on flashing red and green light on aircon unit

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