The idea of an air conditioner freezing at the height of summer seems strange, but it actually happens a lot, and for various reasons. If you notice that your evaporator coils have frozen, you may even be able to fix the unit yourself.

Getting Started on a Fix

As soon as you notice that your air conditioning has frozen up, turn it off and change the fan setting to ‘ON’ so that defrosting can start. Then you can do some troubleshooting to determine the source of the problem. Below are some common causes of air conditioner ‘freeze-up’ and how to fix them.

1. Insufficient Airflow

Indoor evaporator coils can freeze if there is not enough air flowing over them. During normal operation, incoming air loses its heat to the coils, but when flow is minimal, the refrigerant can get too cold and cause the coils to become frozen. Your compressor could also be damaged if this happens, as the refrigerant that returns to it will be too cold.

To check if your indoor evaporator coils are frozen, open the indoor air handler. If this happens to be the case, fixing the problem may be as simple as replacing your air filter, as any clogging can restrict airflow. After replacing the filter, wait until the ice has melted before turning the air conditioner back on.

2. Blocked Vents

Many people close off vents in unused rooms during the summer to reduce the amount of air conditioning needed for their home. Other times, these vents are accidentally blocked by furniture, heavy drapery, and other objects. Blocked vents and registers reduce air flow to the evaporator coils and can cause them to freeze up.

Walk around your home and make sure that none of the system’s supply or return vents or registers are closed off or blocked. If you notice anything, remove the blockage.

3. Evaporator Coils Need Cleaning

Dirty evaporator coils are another common cause of air conditioner freezing. If they are covered in thick layers of dirt and buildup, they won’t be able to absorb heat and cool your home properly. Another byproduct of poorly cleaned coils is a clogged condensate drain line, which could cause water damage around the indoor unit.

Although it is possible to clean the evaporator coils yourself, you should do so only if you know what you are doing. If not, call an licensed air conditioning company with certified HVAC technicians like RCI.

When to Call a Professional

While some causes of air conditioner freeze-up can be corrected by the homeowner, others require professional assistance. These issues require an AC Technician:


Insufficient refrigerant is usually due to a leak in the system. Correcting the leak and recharging the refrigerant requires professional assistance, so call your local HVAC service provider.


When a malfunctioning or broken blower motor does not blow enough return air over the indoor evaporator coils, they will get too cold and freeze. An HVAC technician can confirm that this is the cause of the freezing issue and carry out appropriate repairs.

Prevent your AC from Freezing Up

A good preventive AC maintenance schedule can prevent most causes of air conditioner freeze-up, but when your system literally chills out while temperatures are at a record high, the steps outlined here can help.

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