How to fix a frozen A/C unit



Air conditioners can be a life-saver on a hot summer day. But like all machines, A/C units can malfunction at some point. As ironic as it may sound, frozen air conditioners are more common than you think.

A frozen A/C unit is an often overlooked issue. Many homeowners are not equipped with the knowledge to identify a frozen A/C unit, much less prevent it from happening.

In this guide, we’ll look at why an A/C unit could freeze up, steps to troubleshooting a frozen A/C unit, and how to prevent it from freezing in the first place.


What causes an A/C unit to freeze up?

At first, it might seem difficult to identify why your A/C unit has frozen. Don’t worry, you’re not alone! Let’s take a look at some of the most common reasons for an A/C unit to freeze up.

Low refrigerant

If your air conditioner freezes up, your system may be short on refrigerant, the cooling liquid that chills the air outside before entering your house through the A/C. Your A/C needs to have enough refrigerant to function properly. The compressor, housed in the outdoor unit, uses the refrigerant to push cool air inside your house.

When there isn’t enough cold refrigerant in an A/C system, the pressure within the unit drops. This causes temperatures to drop in the evaporator coils, reaching below the freezing point. When this occurs, the surrounding water vapor might cling to these coils and cause them to freeze. The frost builds on the coils and can eventually become a thick sheet of ice.

Faulty blower motor

The blower motor and fan inside an A/C system assist with blowing air over the coils, which helps to create cold air. If the motor stops working, cold air will stop traveling through the supply vents, causing your A/C unit to freeze. If you hear rattling noises from your A/C unit, your blower motor might be defective.

Not enough power to the fan

In some cases, your home’s electrical system might not be sending enough power to your A/C unit. Air-conditioning units use a lot of energy, so a few parts in the unit might not get the power they need. 

For example, your A/C coils might be getting full power from your electrical system, but your blower motor may not be getting enough power to run at full stretch. As a result, your blower motor won’t function properly, and your A/C unit could freeze.

Poor airflow

Your A/C unit could freeze due to a lack of airflow. Proper airflow allows your A/C to cool every room in the house evenly. Additionally, good airflow leads to adequate air circulation, removing microbes and smells, and improving the overall air quality of your home.

Dirty air filter

Make sure your A/C unit’s air filter is clean. A clogged or dirty filter will impact the airflow. As discussed above, this could lead to several A/C problems, including a frozen A/C unit.

Air-duct issues

Air ducts act as a filter for your A/C unit by keeping out dust and dirt, protecting your A/C from contamination. If an air duct is blocked or leaks, the stored contaminants will also start making their way out, polluting the air. Blocked air ducts also result in poor airflow.

Blockages on coils

When air filters get dirty, the airflow tends to leave dust and residue on the coils in your A/C, which are usually wet from the surrounding moisture in the air. An air conditioner’s interior unit stays cool, so the dust acts as an insulator and sticks to the refrigerant coils easily. Dusty coils can lead to blockages, which means ice will eventually form on them. The more dust and moisture there is, the thicker the ice becomes.


What to do when your A/C unit freezes

Once you’ve identified why your A/C is freezing, there are a couple of things you can do to fix it. 

1. Thaw it out

Turn off the circuit breaker connected to your A/C unit and let the ice thaw. Keep in mind that it could take an entire day for the ice to thaw out completely, so you might want to let it thaw on a day you’re not home. Additionally, be aware of the temperature if you have pets that need the A/C running.

If you and your pets can’t afford to stay away from your house for a whole day, you can leave the blower running with the A/C turned off. However, avoid using your A/C if your coils have ice on them. Frozen coils can damage your A/C unit’s compressor, which is the most expensive part of the unit, costing $1,200 on average, according to HomeAdvisor.

Finally, never use sharp or heavy tools to break up the ice yourself; this will further damage your A/C unit, and you’ll end up spending more money on your A/C repairs.

2. Dry the coils

The next thing you’ll need to do after the ice thaws out is dry the evaporator coils. Turn your A/C on, let the blower run, and set the thermostat to run only the blower motor or fan. This helps circulate the air and lets the coils defrost more quickly. Your A/C unit should function normally once the coils are dry.


How to prevent an A/C unit from freezing up

Frozen A/C units are a common household issue, but there are a few things you can do to make sure your air conditioner doesn’t freeze up again. 

1. Change your air filter

It’s recommended to change your air filter on a monthly basis. However, depending on your usage, this could range from one to every three months. Once you’ve bought a new filter, follow these steps to change your air filter:

  • Remove the grille from your A/C unit
  • Remove the old filter
  • Take out your new filter and align it with the grille
  • Put the grille back and reinstall your A/C unit

2. Schedule regular maintenance to check coolant levels

If you notice the following signs, your A/C unit might have a refrigerant leak:

Every once in a while, hire a professional HVAC technician to perform a comprehensive inspection on your air-conditioning system. The technician will use measuring instruments to check coolant levels and identify any other potential issues. Coolant chemicals are toxic, so it’s best to let a professional handle them. 

3. Get an airflow inspection

A major reason for frozen A/C units is obstructed airflow. Obstructed airflow affects A/C units and impacts the functioning of other cooling and heating systems.

A blocked vent stores all the dirt and residue inside and doesn’t allow the air to flow properly. Without proper airflow, your A/C unit will try to work harder to release cold air. This could lead to malfunctioning.

Sometimes, the ductwork in your home might be installed incorrectly or maybe in the wrong size. Regardless of the cause, you should get an HVAC professional to inspect the clog and your home’s ductwork. The HVAC professional will clear the blockage and any other cause of concern that might harm your air conditioning.

4. Clean the evaporator coils

If your HVAC system collects moisture from liquid or gas and develops a clog in your A/C unit’s airways, the excess liquid can accumulate and turn into a sheet of ice, meaning your evaporator coils could become frozen as well.

Over time, dust, dirt and grime could stick to the ice buildup in the coils and form a clog. Dirty evaporator coils disrupt airflow and cause your A/C unit to malfunction.

The best way to prevent your coils from freezing is to schedule regular maintenance. Alternatively, here are a few easy ways to clean your coils at home:

  • Use compressed air. You can use a hair dryer to do this, but make sure you set it to “fan only” mode. Direct the compressed air in the opposite direction of the regular airflow across the evaporator coil. Make sure you wear eye protection and use a consistent airflow across the coil.
  • Use a brush. Use a soft brush to sweep the dirt off your coils. Avoid using brushes with hard bristles because they can damage the fins. This effective way to clean your coils offers you greater control over the pressure and areas you are brushing.
  • Use water and detergent. Mix a mild detergent with water in a spray bottle and spray it over your evaporator coils. Give the solution a few minutes to sink in to loosen up the dirt on the coils. Wipe off the loosened dirt using a cloth or a soft brush and let the coil dry.


Air conditioners are covered under a Cinch warranty

Whether it’s a faulty motor blower, low refrigerant levels, dirty air filters or blocked coils causing your issues, with Cinch Home Services, you never have to worry about your air conditioner being frozen for long.

Cinch’s home warranty plans cover air conditioners and other major home appliances or built-in systems with award-winning services that help control the costs of breakdowns.

Cinch’s home warranty plans come with instant bookings, all backed by Cinch’s 180-day workmanship guarantee.

Choose from one of Cinch's three warranty plans and get these best-in-class home services. Reach out now for an instant quote.


Ever had your air conditioner throw out ice? Read on to learn how to fix your frozen A/C unit.