Frozen AC Coil: Top Causes and Fixes

close up of frozen ac pipes

If you place your hand over the vents and feel warm air coming from the AC, it could indicate a frozen coil. This issue can make your home feel warm and might lead to water damage due to moisture buildup, potentially causing mold and other problems.

A functioning AC system is essential for your household’s comfort and air quality. AC units not only cool the air but also purify it by trapping contaminants as they circulate through your home. Additionally, a working AC helps prevent excessive humidity, which can damage your furniture and electronics.

The AC coils are responsible for removing hot air from your house, recirculating it, and sending cool air back into it. With a properly functioning AC unit, reaching your desired temperatures is nearly impossible.

In this article, we’ll discuss how to identify a frozen AC coil and ways to fix it.

Table of Contents

Signs of a Frozen AC Coil

When your AC doesn’t work, it could be a number of different issues. Here are the signs that your AC may have a frozen coil.

  • Reduced airflow
  • Warm air blowing from the AC
  • Visible ice on the coil or refrigerant line
  • Unusual AC operation sounds
  • Increased humidity in the home

Causes of a Frozen AC Coil    

You may have frozen AC coils for many reasons, such as the following:

Dirty Air Filter

The air filter must be clean for the air to flow freely through the HVAC system. A dirty air filter obstructs the airflow, which can cause the coils to get too cold, leading to ice buildup and frozen coils.

 Low Refrigerant Levels

If the HVAC system’s refrigerant leaks or isn’t replaced, it may absorb more heat than necessary, which can cause the refrigerant lines and coils to freeze. If the refrigerant is leaking, it’s an emergency repair that requires professional assistance immediately because it could be a danger to your home and the environment.

Thermostat Issues

IIf your thermostat isn’t accurately reading temperatures, it can miscommunicate with your HVAC system, leading to frozen coils. An improperly functioning AC unit may cause the HVAC system to run excessively, damaging the unit and resulting in frozen coils.

Dirty or Clogged Coils

AC coils naturally accumulate dirt and debris from regular use, but if they aren’t cleaned, this can impede airflow. If the AC unit continues to run, the system continues to cool, but the air isn’t exchanged in the coil, which causes it to freeze.

Broken Fans

If the fan motor breaks, the air doesn’t move. If the AC unit continues to run, the cooling happens, but there’s no air to cool, so the coils eventually freeze. This can also occur if the fan blades are dirty and cannot properly move the air.

Fixes for a Frozen AC Coil

If you think you have frozen AC coils, here’s how to fix it.

Before calling an HVAC professional, do these things immediately to fix a frozen AC coil:

  1. Turn the AC unit off

Turning the AC unit off, even on the hottest day of the year, will prevent further damage. This also makes it safer to conduct any inspections.

  1. Wait 24 Hours

Sometimes, the AC coil can defrost on its own. Give it 24 hours to see if the system can defrost itself.

  1. Check the air filter

Check your air filter if it’s been a while since you changed it. A clogged air filter could be the culprit in your frozen coil, and simply switching it could increase the air flow and fix the problem. You’ll still need to defrost the coil if this is the problem, but it’s a step in the right direction.

  1. Turn the fan on

Don’t turn the AC unit on, but only the fan. This allows hot air to circulate through the system and over the coils to help them defrost.

  1. Let the coils dry

After defrosting the coils, make sure they are fully dry. If they aren’t completely dry, the accumulated moisture could cause them to freeze again.

  1. Check the coils

 Before turning the AC back on, check the coils and ensure they are intact and clean. If you are unsure how to clean the coils, consider calling a professional to help. They can also inspect the system and ensure the frozen coils don’t cause any more damage. Rest assured, these steps effectively prevent further issues with your AC unit.

Call an HVAC professional if you take all of these steps and the coils are still frozen. They can address the issues causing the frozen coils beyond changing the air filter or letting the system defrost itself. Professionals can check for refrigerant leaks or other mechanical issues causing airflow problems and reducing your AC’s capabilities.

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How Preventative Maintenance Can Help

Regular HVAC maintenance is key to preventing frozen coils, a common issue often resulting from neglect. By ensuring your system is regularly inspected and cleaned, you can significantly reduce the risk of frozen AC coils, maintaining the efficiency and lifespan of your HVAC system.

Regular Inspections

Have your HVAC system inspected in early spring to ensure everything runs smoothly. During these inspections, an HVAC professional can determine if there are any potential issues or risks that could cause frozen AC coils. They look for specific issues that could impede the airflow and put your system at risk. They will also look for any potential refrigerant leaks or other issues that could make your AC unit not work.

Proper Cleaning Routines

Make sure you change your air filters as often as the manufacturer suggests and more often if you notice they get clogged faster. Also, consider hiring an HVAC professional to clean the AC condensate drain, evaporator coils, condenser, and intake vents regularly.


If you suspect frozen AC coils, it’s crucial to act promptly. You can start by turning off the AC unit and allowing it to sit for 24 hours. It’s best to contact a local HVAC professional for an inspection during this time. Remember, your quick response can help identify and address the issue, potentially preventing further damage to your HVAC system.

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How long does it take to thaw AC coils?

AC coils typically defrost in 24 hours, but it may take longer, depending on the outdoor temperatures. If it’s too warm out, they will not defrost as quickly. If this occurs, it’s best to call an HVAC professional.

Will turning off the AC unfreeze it?

Turning the AC off is the first step in defrosting the coils. Let the system sit for 24 hours before turning the fan on, but only the fan, not the AC unit itself. The fan can circulate the warm air to the coils to help them defrost. However, this isn’t always a quick fix, and a visit from an HVAC professional may still be necessary.

What temperature causes AC to freeze?

If the outdoor air temperature is below 60 degrees, it can cause the air inside your AC to freeze if you run the AC. This is because the pressure inside the unit will build up, and the airflow will be blocked.

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