How to Fix a Frozen AC Unit and Get Cool Air Flowing Again

There’s nothing more frustrating than a frozen AC unit during the hottest months of the year. When your air conditioner starts blowing warm air instead of the cool breeze you expect, it’s often a sign that the unit is frozen. Luckily, learning how to fix a frozen AC unit isn’t as difficult as it may seem. With the right steps, you can get your AC back to working condition without needing to call an expensive technician.

In this post, we’ll guide you through the common causes of a frozen AC unit, how to thaw it out, and how to check for warning signs and prevent future freezing issues. Whether you’re dealing with frozen coils, a clogged air filter, or low refrigerant levels, we’ve got you covered.

Why Do AC Units Freeze?

Several issues can cause an AC unit to freeze, including:

Poor Airflow: Blocked air filters, dirty evaporator coils, or closed vents can restrict airflow, causing your AC unit to freeze.

Low Refrigerant Levels: When there’s not enough refrigerant, the temperature inside the evaporator coils drops too low, causing ice to form.

Thermostat Problems: Incorrect thermostat settings or a malfunctioning thermostat may cause the AC to run continuously, leading to freezing.

Faulty Fan or Motor: If the fan isn’t running properly, it can fail to circulate cool air, leading to frozen coils.

Dirty Evaporator Coils: When dust and debris build up on the coils, it can block the heat transfer process, resulting in freezing.

Knowing the cause of the freeze will help you address the problem more efficiently and prevent future issues.

How to Fix a Frozen AC Unit

Now that we know why AC units freeze, let’s dive into how to fix a frozen AC unit and get cool air flowing again.

1. Turn Off the AC

The first and most important step is to turn off your air conditioner. Continuing to run a frozen unit can cause additional damage, including a blown compressor. Turn off the power at the thermostat, and unplug the unit if possible.

2. Let the Unit Thaw

The next step is to allow the AC to thaw completely. Depending on how frozen the unit is, this could take several hours. You can speed up the process by opening windows and doors to increase air circulation, but avoid using any external heat sources (like hairdryers),as they can cause damage to sensitive parts.

Tip: If you’re in a rush, you can place a fan near the unit to help thaw it faster, but be patient and avoid forcing the ice to melt.

3. Check the Air Filter

Once the ice has melted, inspect the air filter. If the filter is dirty or clogged, it could be restricting airflow, which may have caused the freezing in the first place. Replace or clean the air filter if necessary.

Tip: A clean air filter ensures proper airflow, helping your AC function efficiently and preventing freezing in the future.

4. Clean the Evaporator Coils

If you notice dirt, dust, or debris on the evaporator coils, you’ll need to clean them. Dirty coils can obstruct airflow and cause the temperature inside the coils to drop too low, leading to ice buildup.

To clean the coils, follow these steps:

• Turn off the power to the AC unit.
• Use a soft brush or a vacuum cleaner with a hose attachment to remove dust and debris from the coils.
• Use a coil cleaner (available at most hardware stores) to remove stubborn buildup.

Caution: Be gentle when cleaning coils, as they’re fragile and can be damaged easily.

5. Check for Refrigerant Leaks

Low refrigerant levels are a common cause of frozen AC units. If the refrigerant is low, it could be due to a leak. Unfortunately, fixing refrigerant leaks is a job best left to professionals, as it requires special tools and knowledge of the refrigerant gas used in your system.

However, you can check for signs of low refrigerant, such as:

• Icy buildup on the evaporator coils that reappears quickly after thawing
• Warm air blowing from the vents even when the AC is running

If you suspect low refrigerant, it’s time to call an HVAC professional to diagnose and fix the issue.

6. Check the Fan and Motor

A malfunctioning fan or motor can prevent air from circulating through the evaporator coils, which can lead to freezing. Check to see if the fan is running smoothly. If the fan is making unusual noises or not running at all, the issue could be a faulty motor or fan blades that need repair.

If you find that the fan or motor is defective, it’s important to contact a professional HVAC technician to get it repaired or replaced.

7. Reset the Thermostat

In some cases, a malfunctioning thermostat can cause the unit to freeze. If your thermostat is set too low or is malfunctioning, it can cause the AC to run excessively. Reset your thermostat to the recommended temperature, typically between 72°F and 78°F.

Tip: Consider investing in a programmable thermostat that can automatically adjust temperature settings to ensure your unit doesn’t run unnecessarily.

Preventing Future Freezing

Now that you know how to fix a frozen AC unit, here are some simple preventative measures to keep your unit running smoothly and avoid future freezing issues:

Replace air filters regularly. Change your air filters every 1-3 months to ensure proper airflow.

Clean the evaporator coils. Clean your coils at least once a year to remove dirt and debris that may restrict airflow.

Check refrigerant levels. Regularly check refrigerant levels and have a professional handle any leaks.

Maintain proper airflow. Keep vents open and unobstructed to allow for proper airflow throughout your home.

Schedule annual AC maintenance. Have your HVAC system professionally inspected and serviced at least once a year to catch any potential issues early.

When to Call a Professional

While many frozen AC issues can be resolved by homeowners, there are times when it’s best to call a professional. Consider contacting an HVAC technician if:

• The ice buildup continues to reappear even after thawing and cleaning.
• You suspect refrigerant leaks or low refrigerant.
• The fan or motor is malfunctioning and requires repair or replacement.
• You’re uncomfortable performing any of the repairs yourself.

A qualified technician will diagnose and fix the issue quickly, saving you time and preventing further damage to your system.

By following the steps outlined in this guide like checking your air filter, cleaning the evaporator coils, and inspecting the fan and motor. You can potentially restore cool air to your home in no time without spending a ton of cash hiring a professional. 

However, for more complex issues like refrigerant leaks or a faulty fan motor, don’t hesitate to reach out to a professional. At Liberty Home Guard, we offer comprehensive home warranty plans that include HVAC coverage, so you don’t have to worry about unexpected repairs.