How to Unfreeze Your Air Conditioning System

Do you see ice on your indoor or outdoor unit? If so, immediately stop running your AC system and follow the below instructions to prevent damaging the compressor. Repairing a compressor is on the high end for HVAC costs because a dysfunctional compressor leads to a dysfunctional AC system as a whole. Learn more about “What Is a Central AC Compressor” in our blog.

To thaw out your AC system and get it back to normal, attempt these 3 main steps:

In this article, we’ll explain why the above steps are important and how you can use them to prevent ice buildup in the future.

Ice on the AC unit typically means that your system has one or both of these two problems:

• There is not enough airflow entering your AC system
• There is a leak in the evaporator coil or refrigerant lines

Either problem means that the refrigerant inside the evaporator coils has nothing counteracting its low temperature (refrigerant is a cold chemical agent that cools your home’s air and travels between the indoor and outdoor units). Therefore, it ends up freezing the system instead of doing its job.

This ice over can negatively impact your AC compressor located in the outdoor unit and other fragile components. Turn off your thermostat’s cooling cycle to stop your AC from trying to send the super chilled refrigerant to the outdoor unit.

Want more in-depth information about why your AC is freezing up in the first place? Just check out our blog, “Why Is My Air Conditioner’s Refrigerant Line Covered in Ice?”.

Next, you’ll want to turn your thermostat fan settings to ON. This forces the AC’s indoor blower fan to circulate warm air nonstop over the ice, leading to a faster thaw.

How does this work? Well, if you’ve ever experienced your AC blowing warm air instead of cold air, the thermostat was probably set to AUTO. The ON setting keeps the blower motor running whether or not your AC is actually cooling the air. Therefore, if the AC is no longer cooling, it will only blow warm air throughout your home.

A clogged air filter is the most common culprit behind a frozen air conditioner—and many other problems. Check the filter as soon as you turn the thermostat to OFF. If you wait too long, the ice might melt and combine with the dirt on the filter, creating a dirty puddle to clean up.

You can find the filter near your thermostat in a return duct or next to the air handler. An air filter that looks like the above picture needs immediate replacement. Dirt and debris on the air filter “suffocate” your air conditioner because insufficient air enters the system. Not enough air coming in means not enough cooled air coming out. The unit gets colder and colder without enough warm air making contact with the evaporator coil housing the refrigerant. Also, keep in mind that the AC can only chill the amount of air it takes in.

Learn how to change out the filter in our blog, “Where Is My AC Filter Located and How Do I Change It?”

Essentially, frigid evaporator coils combined with any moisture in the air produce ice. It can be surprising to learn that many frozen AC units occur in Phoenix during the monsoon season. You might think, “isn’t that during our hottest months?” Yes, but monsoon season comes with more humidity in the air. Preparing your AC and home for monsoon season can help reduce humidity and prevent ice buildups in the future.

Is your air filter clean? In this case, wait until your AC has thawed out. Depending on the AC system's size and the severity of the ice buildup, it can take anywhere from 1 to 24 hours to unfreeze fully. After you turn the system back on, continue to monitor the system for the next few days and see if any ice returns or other AC problems.

A frozen system with a clean air filter indicates that you have a more severe AC problem on your hands. If you notice any ice forming or other issues, call a professional to inspect and diagnose your unit ASAP to prevent a broken compressor.

These issues can include:

• A refrigerant leak
• Dirty evaporator coils
• Stuck or closed expansion valve
• Collapsed ducts
• An overflowing drain pan
• A clogged condensate drain

All of which can cause your AC to leak water. As we mentioned above, moisture combined with a cold evaporator coil causes ice buildup. Learn more about "Why Is My AC Leaking Water" in our blog. A professional HVAC technician will inspect your system for the cause and repair it.