Ice buildup on an air conditioner can be a challenging issue for homeowners, and the question we always hear is, “Why is my AC frozen.” A frozen AC can impact the cooling efficiency of your AC unit and cause potential damage and costly repairs if not addressed. Understanding the causes of this ice formation is crucial for resolving the problem and maintaining your air conditioning system’s longevity and optimal performance.

If you’re wondering how ice can form on your AC system despite record-breaking temperatures. The answer lies in one of the system’s main components – the evaporator coil.

What does the evaporator coil do?

An evaporator coil is part of an air conditioner or heat pump that absorbs the heat from the air in your house. It is located inside the air handler or attached to the furnace. The role of the evaporator coil is to hold the chilled refrigerant that the compressor moves into it.

As the air from the blower fan moves over the coil, the cold refrigerant removes the heat from your home’s air. The refrigerant becomes warmer and travels to the condenser coil outdoors.

With a heat pump, the process reverses in the winter, and the evaporator coil expels heat from the refrigerant into your home instead of absorbing it and taking it outdoors. Most heat pumps have auxiliary heating elements that are part of the evaporator coil components to supply heat when temperatures fall below a certain point.

In simpler terms, the coils hold the cold refrigerant and remove the heat from the air as it passes over them. For heating, the process is essentially reversed, creating heat from the air and pushing it into your home instead of removing it.

Now that we have a basic understanding of what an evaporator coil is and its role in cooling your home, let’s talk about some culprits that can lead to a frozen evaporator coil.

Causes of a Frozen AC Unit

Lack of Air Flow

First up, and most commonly, lack of airflow. As stated above, the evaporator coils absorb heat from the air. But if they don’t have enough heat to absorb, the condensation on the coils can freeze. Low airflow can be caused by dozens of problems within the AC system, such as a malfunctioning blower fan, dirty filters, or even damaged ductwork.

Dirty Evaporator Coil

Too much dirt and debris can impact dirty evaporator coils, obstructing the heat exchange process. Dirty coils are less efficient at absorbing heat from the air, causing the condensation to become too cold and freeze. Have you ever had your evaporator coil cleaned? Many customers have never even set their eyes on the evaporator coil, but the ones who have usually elect to have it cleaned. Call our office at 813-800-2665 and inquire about your various options for cleaning your coils.

Dirty Air Filters

If your air filter gets clogged or dirty, it can limit the airflow to your evaporator coils. This can cause the coils to become excessively cold and freeze up. To avoid this issue, changing your AC filter every 30 days is best. If you have a washable AC filter, clean it every 30 days. TIP: If you have two washable filters, you can replace the dirty one with a clean filter while you wash and dry the dirty filter. Running your AC without a filter can result in dirty or clogged coils, which will cost you more for AC repairs.

Damage Ducts and Closed Vents

Closed or obstructed vents can lead to insufficient airflow, resulting in ice buildup.

Faulty Blower Motor

A malfunctioning blower motor can cause inadequate airflow, leading to ice formation on the AC unit. If the blower motor is not functioning properly, it may not be circulating enough air over the evaporator coils, causing them to freeze.

If you suspect that you may have airflow issues, schedule an inspection of your air conditioning unit sooner rather than later to avoid an uncomfortable breakdown and potentially costly repairs.

Low Refrigerant Levels

Low refrigerant levels can lead to frozen evaporator coils. Low refrigerant causes the system to overwork, freezing condensation on the coils. AC units work on a closed system, meaning refrigerant doesn’t simply run out. Therefore, the problem is either a refrigerant leak in your system or an insufficient charge if the low refrigerant is low. Low refrigerant isn’t uncommon and is checked during our routine HVAC maintenance visits. Not sure where your refrigerant levels are currently?

If your house is cooling well, you probably have decent refrigerant levels, but if your AC is struggling to get to temperature, it could be partially to blame for your cooling problems.

Clogged Drain Line

It is possible to have a frozen evaporator coil AND a clogged drain line. A clogged drain line could certainly hinder the proper functioning of your AC system, causing it to work harder and creating too much condensation to form on the coil, which can freeze.

Outdoor Temperature

When the outdoor temperatures are lower than 60 degrees and your air conditioner is still operating, the evaporator coils can become too cold, causing condensation to freeze and form ice.

How to Fix Ice on an AC Unit

Let’s briefly discuss some solutions to get you back to cool and comfortable!

Hiring a professional to fix a frozen AC coil is necessary for several reasons, as a frozen AC will not fix itself. First, the technician will be able to diagnose the problem and determine the exact cause of why the coil is frozen. This information will help them determine the best course of action to unfreeze it and prevent further problems. Additionally, HVAC professionals have access to specific tools and equipment that can help repair or replace system parts that may be malfunctioning or broken. Lastly, professional AC technicians have the experience and knowledge to ensure the work is done correctly and efficiently.

Important Note: Our technicians cannot work on a frozen coil, and it is our preferred method to shut the unit off until the coil is thawed, which can take up to 24 hours. Once thawed, give us a call.

Regular maintenance for an air conditioner includes cleaning or changing the filter, checking refrigerant levels and other mechanical components, and ensuring that all parts are functioning properly. Keeping these components in good condition can reduce the chances of your AC unit freezing up or struggling to keep your home cool.

If you haven’t had a maintenance call yet or want to become a maintenance plan customer, let me remind you of our new and improved maintenance plan offerings! Each plan level has different offerings to provide affordable maintenance solutions for everyone!

Here is the link to our AC Maintenance Plans, or call 813-800-2665 to learn more.

We look forward to continuing to be your dedicated HVAC solutions provider bringing our customers quality, integrity, and reliability with a smile!