A frozen AC in the middle of summer is one of the most alarming sights in the home but not necessarily one of the most serious.

Seeing your AC coils frozen might trigger panic but most problems have relatively simple answers, such as:

A frozen AC won’t fix itself, but a solution should not be far away. Let’s find out more about the main issues, how to tell if AC is frozen, how you can fix it, and how to prevent it from happening again.

WHY IS YOUR AC FROZEN?

Air conditioning units are most likely to ice over when they’re working their hardest. That’s generally when the temperatures are highest. 

In Florida, it’s usually the indoor AC unit that freezes up during the cooling process. As the air conditioner removes heat and humidity from the indoor air, water collects on its evaporator coils. This should drip off and be channeled away outside, but if it collects on the cold, refrigerant-heavy coils for too long and doesn’t drip off, it may turn to ice.

A frozen AC usually happens for one of a few reasons:

Let’s look at each reason in more detail.

INSUFFICIENT OR BLOCKED AIRFLOW

Efficient AC systems work with a specific balance of airflow and pressure. 

Airflow can be restricted by:

If the system suffers from any of these issues, it cannot effectively remove warm, moist air from the home, sometimes leading to frozen condensation on the coils and frost or ice forming. 

LOW REFRIGERANT LEVELS

Your AC system uses refrigerant gas for the air-cooling process. This unique chemical is highly sensitive to pressure variations in AC systems.

AC is a closed system but a leak in the refrigerant lines can reduce levels (Note: Most AC refrigerant is almost odorless, so check out this post for the signs of a refrigerant leak).

A blockage could also mean that refrigerant doesn’t flow through the system properly. 

This can lead to:

AC refrigerant should only be handled by licensed professionals. Don’t attempt to fix a refrigerant leak yourself.

BROKEN FAN 

All components of an AC system must work in sync for efficient cooling. 

If the evaporator fan develops a fault, spinning too slowly or not at all, airflow across the coils is reduced, causing moisture to linger and freeze. 

If you suspect a fan issue, professional AC repairs are the safest fix. Regular AC servicing is the best way to catch this problem before ice ever forms.

BLOCKED CONDENSATE LINE

A frozen AC can also be due to a blocked condensate drain, though this is a less common cause.

As your central AC runs, it pulls humidity from the indoor air, as you know. That moisture collects on the evaporator coil before dripping into a drain pan and exiting through a condensate drain line. 

If the drain line becomes blocked by algae, debris, or dirt, water backs up in the pan and around the coil. Combined with the cold refrigerant already running through the coil, this excess moisture can quickly turn to ice.

HOW TO TELL IF YOUR AC IS FROZEN

In Florida, visible ice most commonly forms on the evaporator coil of the AC unit, which is usually in the air handler in the interior unit. 

Less obviously, ice can also form in other parts of an AC system, especially after a refrigerant leak, when ice-cold fluid may pour into the section of the unit below the evaporator coils. 

You should check your AC system for ice if:

WILL A FROZEN AC FIX ITSELF?

A frozen AC won’t generally fix itself but a solution shouldn’t be too far away. In most cases, the cost of AC repairs shouldn’t be too high, although serious refrigerant line problems can be costly.

Let’s first look at what you can do before calling the AC pros.

HOME FIXES FOR A FROZEN AC

First, you need to get rid of the ice by thawing it:

1. Switch off the power to the AC unit
2. If it’s summer, the ice should thaw quickly but you can place a standing fan nearby to speed the process up.
3. Empty the drain pan as needed (the melted ice drips into the drain pan and will quickly fill it, so beware of overflowing water that can cause damage to your home).
4. Wait until all the ice has thawed naturally. Don’t try to chip it off with a knife, which can damage components.

CHECK AND CHANGE THE AC FILTER

Once the ice has thawed, change your AC filter if you haven’t done so for two or three months. From our experience across the Southwestern and Central Florida region, dirty, clogged filters are the #1 cause of AC problems here:

1. Turn off the AC.
2. Locate the AC filter. It’s usually between the return duct and the air handler, a large metal box that houses the fan and its motor in central AC systems. 
3. Slide the dirty filter out and discard responsibly.
4. Replace it with a new filter, making sure the new one is the right size and is inserted correctly (an arrow on the packaging or filter itself will tell you which way it goes).
5. Turn the AC back on and see if the system freezes up again over the next few days.

INSPECT THE AC COILS

If you’re feeling adventurous, you can check the AC evaporator coils, which help to remove heat from the indoor air.

Sometimes, dust and dirt can make their way to the coils and cause a lack of airflow.

1. Turn off the AC.
2. Locate the coils in the indoor air handling unit near the blower motor. 
3. If they appear dirty or clogged, contact us to book an AC tune-up, which is likely overdue anyway.

WHEN TO CALL AN AC PROFESSIONAL

If the frozen AC doesn’t resolve itself from changing the filter or removing obstructions from the vents, an HVAC professional will perform some basic AC troubleshooting to identify the root cause.

The key is to tackle problems early to prevent more serious issues, like damaged parts (a cracked coil or broken fan from hitting the ice). 

Often, a simple tune-up can resolve the problem.

FAQs

The cost of AC is high enough already in Florida without letting minor problems turn into major ones. Get your AC unit’s ice problem diagnosed and fixed before it runs up your repair bills.

If you’re in SW or Central Florida and have a problem with a frozen AC system, contact us to arrange a full inspection and fix.