7 Common Causes of a Frozen Evaporator Coil

Installed Heating and Cooling System - Frozen Evaporator CoilWhen the weather heats up, your air conditioner is essential for staying cool. But sometimes, your AC can get too cold, leading to a frozen evaporator coil and problems with your air conditioning unit.

Understanding this issue is important. Seven common causes of a frozen evaporator coil include lack of airflow, dirty air filters, dirty evaporator coils, refrigerant problems, low outdoor temperatures, clogged AC drain lines, and improper installation.

In this article, we’ll dive into these causes and explore effective solutions to keep your AC running smoothly.

What is an Evaporator Coil?

The AC evaporator coil is an important part of your AC unit. It’s where the magic happens—where heat is absorbed from your home’s air.

During the cooling process, the coil’s refrigerant absorbs the heat from the air, turning it from a liquid to a gas. This cools the air that’s blown into your home. In heating mode, the process reverses. Understanding this process helps us grasp why a coil might freeze.

What Causes an Evaporator Coil to Freeze Up?

Lack of Airflow

Low airflow can wreak havoc on your evaporator coils. Without sufficient air moving over the coils, they can’t absorb heat effectively. Common causes include a malfunctioning blower fan, dirty air filters, or damaged ductwork. When air can’t flow freely, it disrupts the heat exchange process, leading to freezing.

Dirty Air Filter

A dirty clogged air filter is a classic culprit. It restricts airflow, causing the coils to get too cold and freeze. Additionally, dirty filters spread dirt throughout the system, clogging other parts and reducing efficiency. Changing your filter regularly can prevent this issue.

Dirty Evaporator Coils

Dirt and debris on the evaporator coils block the heat exchange process. When coils are dirty, they can’t absorb heat properly, leading to frozen condensation. Keeping your coils clean is key to maintaining cooling efficiency.

Refrigerant Problems

It may seem odd, but low refrigerant levels can cause your coil to freeze. The refrigerant in your AC is a closed system, so low levels typically indicate a leak or insufficient charge. When there isn’t enough refrigerant, the coils get too cold, causing ice to form.

Lows Temperature Outside

If the outdoor temperature is too low, your evaporator coil might struggle to absorb enough heat. This can lead to condensation freezing on the coils. It’s a common problem when running the AC on cool nights.

Clogged AC Drain Line

Your AC unit naturally produces condensation, which is drained away through the AC drain line. If this line gets clogged, excess condensation can freeze on the evaporator coil. Regularly checking and cleaning the drain line can help prevent this.

Improper Installation

Incorrect installation can lead to various issues, including frozen coils. If your AC system isn’t set up correctly, it can affect airflow and refrigerant levels, causing the coil to freeze. Always use a professional for installation to avoid these problems.

How to Unfreeze an Evaporator Coil

Thaw the Coils

First, you’ll need to thaw the coils. Turn off your air conditioner and switch to “fan only” mode. This will help melt the ice without causing further damage. Be patient; it can take a while for significant ice buildup to melt.

Replace the Air Filter

If your air filter is clogged or dirty, replace it. This simple fix can restore proper airflow and prevent further freezing. Once the system has thawed, resume normal operation and keep an eye on the filter’s condition.

Clean the Coils

Cleaning the evaporator coils can be a DIY task if you’re up for it. Here’s how:

  1. Turn off the AC system.
  2. Locate the coils.
  3. Mix warm water with detergent.
  4. Apply the solution to the coils, let it sit, then wipe away the debris. If you’re unsure, it’s best to call a professional to ensure the job is done right.
  5. Call a Professional

Professional help is often the best route for a thorough inspection and repair. A trained HVAC technician can diagnose and fix underlying issues, ensuring your air conditioner works seamlessly.

How Preventative Maintenance Can Help

CJS Heating & Air Technician Preventative maintenance is essential for a long-lasting AC unit. Regularly changing air filters every 60-90 days and scheduling annual professional inspections can keep your system in top shape. Consider maintenance before the summer and winter seasons for optimal performance.

CJS Heating & Air Can Help

We offer a range of services, including evaporator coil maintenance and other AC repairs. Let us keep your home comfortable all year round.

Final Thoughts

Understanding the common causes and solutions for a frozen evaporator coil can help you maintain your AC unit effectively. Regular maintenance is key, and professional assistance ensures comprehensive care. Keep cool and comfortable by staying on top of your air conditioning needs.


Why does an evaporator coil freeze?

Evaporator coils freeze due to restricted airflow, dirty coils, low refrigerant levels, low outdoor temperatures, clogged drain lines, or improper installation.

How can I tell if my evaporator coil is frozen?

Signs of a frozen evaporator coil include reduced airflow, visible ice on the coils, and your AC struggling to cool your home.

Can I fix a frozen evaporator coil myself?

You can try thawing the coils and replacing dirty air filters. However, cleaning coils and handling refrigerant issues are best left to professionals.

How often should I change my air filter to prevent freezing?

Change your air filter every 60-90 days to maintain proper airflow and prevent coil freezing.

What should I do if my evaporator coil keeps freezing?

If the problem persists, call a professional HVAC technician to diagnose and fix the issue. There may be underlying problems that require expert attention.

How does low refrigerant cause the evaporator coil to freeze?

Low refrigerant levels cause the evaporator coil to become too cold, leading to ice formation. This usually indicates a leak or insufficient refrigerant charge.

Is regular maintenance really necessary?

Yes, regular maintenance prolongs the lifespan of your AC unit and helps prevent issues like frozen evaporator coils. It’s a small investment for long-term comfort and efficiency.