Why your AC freezes up

An air conditioner freezing during the hottest day of the year may sound out of the ordinary, but it often happens, and a frozen system can turn a fine day into a miserable one. You might not understand why this happens or how to resolve it. 

How to check

If you take a look at your supply vents and discover that they’re warm to the touch, it’s a sure sign that there may be freezing. Open up the panel at your return and take a look behind the air filter. While you may not always see ice on the evaporator coils, if you do, you’ll undoubtedly need to take action. 

Causes of evaporator coils freezing

To prevent freezing, air conditioners need continuous airflow through the system to prevent moisture build-up on the coils caused by humidity. Two practical preventative methods include 1. Replacing the air filter regularly to alleviate airflow problems and 2. Keeping all windows closed while the system is actively cooling the space. 

How to fix

If you do run into a freezing problem, the first thing you must do is turn off the system to allow it to defrost. After a few hours, turn on only the fan and allow air to circulate for one hour. While you wait, replace the air filter with a new one. After the process is complete and the coils look dry, you can turn the AC back on. 

Mechanical problems and refrigerant leak

Air systems have many moving parts that can get stuck, kink, clog, leak and break. With any one of multiple issues, the air pressure will drop, causing the refrigerant to expand too much. This follows with the freezing of the coils. Many fixes are temporary, and some are cheaper than others, but sometimes, replacing the system might be the best option for longevity and efficiency. 


A frozen air conditioner can be a common occurence. Take the proper measures and replace your air filter often. Leave windows closed while the air conditioner is running. Turn off the system and open windows on cold nights. Preventative maintenance will help you make sure you never have to worry about sweating due to a frozen air conditioner.