With the long, hot days of summer fast approaching, it’s time to turn off our heaters and fire up our air conditioners. As temperatures rise, it becomes more and more important to have a fully functioning AC. But just like any component of an HVAC system, issues can arise. One problem you might encounter is a freezing AC. It can be a puzzling issue to troubleshoot. How is this even possible in the midst of the hottest days of the year?

Air conditioners freezing over can be a fairly common problem. There are a few reasons you might encounter this phenomenon. Let’s explore why it might happen and what to do about it.

How Can You Tell If Your AC Is Freezing?

One of the first symptoms you might notice is that your air conditioner is constantly running but the temperature isn’t changing. It might even get warmer. Another sign to look out for is a lack of airflow. If the air coming through your supply register is weak or undetectable, this means you have an airflow issue. You can identify a lack of cold airflow if the supply register vents are warm to the touch. All of these symptoms will point to frozen evaporator coils.

What Can Cause Your AC Coils to Freeze?

When you notice frost on and around the components of your AC, that points to an issue with the evaporator coils. This part of the system is tasked with cooling down the air in your home. The compressed refrigerant in its liquid state absorbs heat as air from your home passes by the coils. The refrigerant will absorb thermal energy from the air and turn it into a gas. Once this exchange happens, the cool air is blown into your home and the gaseous refrigerant is funneled back towards the compressor and condenser to enter a liquid form again.

This cycle can be interrupted by several issues. But when the evaporator coils are involved it could result in your AC freezing over. Essentially, when the evaporator coils malfunction the refrigerant can get too cold. If the refrigerant dips below its freezing point, the coils can freeze over with condensation.

Here are some of the issues that might cause this:

Blocked Airflow

Proper airflow is a crucial part of a functioning air conditioner. The evaporator coils need warm air to flow through the return air duct to convert the refrigerant from a liquid into a gas. No airflow equals no thermal exchange. Without proper airflow, the refrigerant will remain cold, causing any humidity that settles onto the coils to freeze.

There are a few culprits that can cause a lack of airflow. First, check your supply registers. You should never have more than 2 – 3 vents closed at a time. Also, be sure you don’t have furniture blocking these supply vents.

If this isn’t the issue check in on your air filters. If they’re dirty, they can significantly reduce your system’s ability to circulate air. You should change your filters out at least every 6 months if not sooner (dependent upon MERV rating).

Finally, if you troubleshoot these two issues and there still isn’t sufficient airflow, you might have a blower fan issue on your hands. Your blower could cause issues if it stops working due to wear and tear, its rotational direction is wrong, the rotation speed isn’t correct, or if its power output is fried.

Refrigerant Leak

Since refrigerant plays a major role in the function of the evaporator coils, it makes sense that a leak could cause issues here. This is commonly the issue when you notice your AC frozen over. Low levels of refrigerant can cause the remaining chemical compound to expand and become too cold. There are a few areas where your refrigerant could be leaking. Check the refrigerant lines and evaporator coils first. If these seem intact, take a look at other components that regularly handle refrigerant such as the compressor. If there is a leak, you will likely need to replace the whole system.

Issue With Condensate Drain Line

As you now know, the evaporator coils cool air by absorbing its latent heat. Once the refrigerant goes back to the compressor to get turned back into a liquid, the AC will transfer any absorbed heat outdoors. The system will also simultaneously remove moisture. This moisture will end up in a condensate drip tray and eventually drain through the condensate drain line. Sometimes this line can clog and the tray will overflow. When this happens, the added humidity increases the likelihood that your evaporator coils will freeze over.

Cold Summer Nights

Air conditioners are calibrated to operate within an optimum temperature threshold. If the air it’s handling dips below this threshold, it can cause issues. Cold air won’t exchange the necessary amount of heat with the refrigerant inside the evaporator coils, which could lead to freezing. Programmable thermostats can help your system shut down when the air is too cold. If you don’t have one, take note of how cold it will get that night and shut your system down ahead of time if it’s going to drop below 60 degrees.

If All-Pro Heating and Air can help… We would be happy to check on your unit. When this problem persists or is left ignored, it can do plenty of damage to your unit that will require a costly repair or high-ticket replacement.