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Updated: June 2025

It’s important to periodically inspect your AC unit to ensure it is running smoothly. Checking throughout the year allows you to spot early warning signs should there be any issues with your air conditioning.

One such sign is visible ice forming on an AC unit. An AC ice-up indicates a problem with your system, which can be caused by a number of factors. Below, we’ll look at the cause of ice buildup on an AC unit and possible solutions.

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Ice Inside the Air Conditioner: Is It Normal?

Spotting ice on your air conditioner, whether inside the unit or on the outdoor condenser, is a warning sign that something’s wrong. 

The most common place for ice to form is the evaporator coil. The evaporator coil is located inside the air handler or furnace, usually behind a removable panel. If airflow is restricted or refrigerant is low, condensation on the coil freezes, forming a layer of frost or solid ice.

You might also see frost or ice building up along the copper refrigerant lines (usually the larger, insulated ones) connecting the indoor and outdoor units.

Though less common, other components can be prone to ice buildup. You might notice ice forming on or around the outdoor unit, which can happen when the system struggles to release heat due to refrigerant issues, low airflow, or malfunctioning components. In rare cases, ice buildup can extend into the blower compartment or show up as chunks being expelled from vents. If you notice your air conditioner spitting out ice, that’s a clear red flag.

What Causes Ice Buildup on Air Conditioner Coils?

Your air conditioner has two coil components: the condenser coil and the evaporator coil. If the evaporator coil becomes too cold, the moisture in the air freezes on its surface, leading to frosting and ice buildup. Common causes of ice on the coils include:

• Low refrigerant
• Dirty air filters
• Poor airflow
• Faulty blower fans
• Blocked return vents.

Frozen coils are a common air conditioner issue, so they can be reasonably easy to resolve. While a DIY fix is doable, if the problem persists, it could indicate more serious issues that require an HVAC technician.

How to Fix a Frozen AC Coil

Before dealing with a frozen evaporator coil, make sure you turn off the system completely to prevent damage and keep yourself safe. You’ll need to allow the unit time to thaw completely, and your unit may have a dedicated natural air or fan mode to use during this time.

After thawing the frozen air conditioner coil, check the filter and, if necessary, replace it with a new one. If a clogged air filter was the problem, this simple fix may solve your frozen coil problem.

If the coil freezes again after defrosting and restarting your AC, the unit may have a bigger problem. Contact an HVAC technician for a full inspection and diagnostic.

Signs Your Air Conditioner Has a Refrigerant Leak

Ice forming on your AC unit outside or even inside your system could be one of the signs your air conditioner has a refrigerant leak. When refrigerant levels drop, the evaporator coil can get too cold, causing moisture in the air to freeze on the coil rather than cool your home effectively. This often leads to visible frost or ice forming on the refrigerant lines or coil.

Another common sign is your air conditioner spitting out ice particles through the vents as ice is melting and breaking off inside the unit. You might also hear a faint hissing sound from the indoor or outdoor unit, pointing to refrigerant escaping from a crack or hole in the line.

Aside from physical signs, you may notice your system running longer than usual without effectively cooling your space. Warm air blowing from vents, even when the thermostat is set low, can also signal a refrigerant issue. If left unaddressed, a leak can lead to major damage or even a complete system failure. Prompt attention from an HVAC professional is the best course of action if you suspect a refrigerant problem.

Can Dirty Filters Cause an AC to Ice Up?

Yes, dirty filters restrict airflow, which drops the coil temperature and leads to freezing. Dirt in general is detrimental to your air conditioning’s functionality, whether it’s a dirty air filter or dirty evaporator coils.

Another key part of HVAC maintenance for ice buildup is replacing your air filter regularly, ideally every month during high-use periods. A clogged filter reduces airflow, which can cause the coil to drop below freezing and accumulate ice. Clean filters, on the other hand, allow your system to “breathe,” maintaining the right temperature and efficiency. Make sure you choose the right air filter size so your HVAC can work properly.

HVAC Maintenance Tips to Prevent Ice Buildup

Regular HVAC maintenance is one of the most effective ways to prevent ice buildup on your AC unit and keep your system running efficiently, especially during the peak cooling season. When overlooked, minor issues like a dirty filter or low refrigerant can quickly lead to much larger problems, including frozen coils and serious system damage.

Seasonal tune-ups are essential. A professional HVAC technician will thoroughly inspect and clean the system, ensuring unrestricted airflow and components are working as they should. These visits often include checking refrigerant levels, a critical step in avoiding ice inside your air conditioner.

Technicians also clean coils, fans, and drainage lines to remove dust, debris, and mold that could interfere with the system’s operation. When these parts stay clean, your air conditioner is less likely to overwork or freeze up. By staying consistent with HVAC maintenance for ice buildup, you’ll not only extend the life of your system but also avoid uncomfortable breakdowns during the hottest days of the year.

When to Call a Pro for Ice on Your AC Unit

You should never attempt DIY repair of refrigerant leaks in your air conditioner. Refrigerant is toxic and must be handled by a professional. It also requires proper disposal, which a certified HVAC technician will take care of.

If your air conditioner is spitting out ice, call a professional immediately. This is not an HVAC issue you can DIY fix without potentially damaging the system or making problems worse. If your system continues to freeze even after filter replacement or the ice returns quickly after thawing, you may have reached the extent of home repairs and need a professional to take care of it.

For a comprehensive list, check out our guide, When to Call a Professional Vs DIY HVAC Repairs.

Schedule an AC maintenance visit or inspection with A-Abel today
to avoid bigger (and more expensive) problems later.