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Why is My Air Conditioner Freezing Up? 4 Causes and Solutions

July 19, 2023

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why is my air conditioner freezing up

Having an air conditioner freeze up is a common problem that can occur for a variety of reasons. When ice builds up on the coils, it hinders the AC's ability to properly cool your home. Identifying the cause of the freeze-up is key to restoring normal operation. 

Why is my air conditioner freezing up? Typically, an AC unit will freeze as a result of low refrigerant levels, a dirty filter, thermostat issues, or restricted airflow across the evaporator coil. 

Diagnosing the root of the problem and addressing it quickly can get your AC back to cooling efficiently. In this article, we will look at four common causes of air conditioner freeze-ups and the best solutions for each one.

1. Low Refrigerant Levels

One of the most common reasons an air conditioner freezes up is because it has low refrigerant levels. Refrigerant is the substance that flows through the AC system to remove heat from your home. When refrigerant levels get too low, it can cause the evaporator coils to freeze over. This blocks airflow and prevents the AC from cooling properly.

Signs of low refrigerant include reduced cooling, higher utility bills, and ice buildup on the coils. If you suspect low refrigerant, contact an HVAC technician to inspect and recharge the system. Properly recharging the AC with refrigerant can solve the freezing issue and restore cooling.

2. Dirty Air Filter

A dirty, clogged air filter can also cause an AC system to freeze up. The filter is responsible for removing dust, allergens, and debris from the air. But over time, it gets overloaded and blocks airflow across the evaporator coil.

This starves the coil of airflow needed to absorb heat. The lack of airflow causes the coil to operate at below-freezing temperatures, resulting in ice formation.

Replacing a dirty filter allows air to flow freely again. This regulates the temperature, prevents freezing, and improves cooling. Air filters should be replaced every 1-3 months for optimal performance.

dirty air ducts

3. Why is My Air Conditioner Freezing Up? Maybe a Faulty Thermostat is to Blame

Problems with the thermostat settings can lead to freezing as well. If the thermostat is set too low, it will force the AC unit to run constantly. This overworks the system, drives down coil temperatures, and can ultimately lead to freezing.

A faulty thermostat that is miscalibrated can also trigger freezing issues. It may give inaccurate readings and call for excessive cooling. Inspect your thermostat settings and calibration to ensure proper operation. Adjust as needed to prevent over-cooling.

4. Low Airflow Across Coils

Finally, restricted airflow across the coils can allow ice to accumulate. Clogged ductwork, blower motor problems, fin damage, and more can reduce airflow. This prevents warm air from properly melting off frost buildup on the coils.

Professionally cleaning the ducts, fixing blower issues, and repairing bent coil fins can all help increase airflow. This keeps air circulating correctly across the cold coils and reduces freezing potential. Contact an HVAC technician if you notice any airflow obstructions.

Winding Down

An air conditioner freezing up can be frustrating, but identifying the root cause is the first step toward resolving the issue. Low refrigerant, dirty filters, thermostat problems, and restricted airflow are the most common culprits. Schedule yearly maintenance to help prevent freeze-ups and catch any problems early. 

If your AC does start freezing, address any underlying issues like recharging refrigerant, changing filters, adjusting thermostat settings, or removing airflow obstructions. Taking the proper steps to fix the cause of the freeze-up will get your air conditioner back to working order and cooling your home comfortably. With regular maintenance and prompt attention when freezing does occur, you can minimize AC disruptions during the hot summer months.

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When it comes to customer service, Cypress AC Repair Pros are the best! With decades of on-the-job training and excellent work ethic, our clients can have peace of mind with our team on the scene. To get in touch with us right now, please call (281) 746-6952. We'd love to speak with you.


How do I stop my air conditioner from freezing?

The best way to prevent an air conditioner from freezing up is to have it serviced annually to check for refrigerant levels, clogged filters, airflow issues, and thermostat calibration. If freezing does occur, calling an HVAC technician promptly to diagnose and address the specific cause, whether low refrigerant, dirty filter, airflow restriction, or thermostat malfunction, can get the unit back to cooling properly.

How do you unfreeze an air conditioner fast?

To rapidly unfreeze a frozen air conditioner, you can try setting the thermostat to fan mode, which will allow warm air to circulate across the frozen coils and help melt the ice. You can also try turning the air conditioner completely off for a few hours so the ice can melt, then turn it back on once the coils thaw.

Will my AC work again after it unfreezes?

Once an air conditioner has thawed and unfrozen, it should be able to resume normal operation and cooling. However, it's a good idea to have an HVAC technician inspect the unit to diagnose and repair the underlying issue, like low refrigerant or airflow restriction, that originally caused the freeze-up to prevent recurrence.

Does turning heat on help to unfreeze AC?

Turning on the heat can help unfreeze an air conditioner as it circulates warm air across the frozen evaporator coils to melt the ice buildup. However, leaving the AC unit off for a few hours allows it to naturally thaw, and using a fan to blow air over the coils works more quickly than heat, so those methods are typically better options for unfreezing a frozen AC.

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