What Causes Air Conditioner Freeze-Ups?



When ice forms on air conditioning units, it robs them of their ability to cool. These freeze-ups can lead to expensive repairs. That’s why it’s critical to understand the causes of freeze-ups and the steps you can take to prevent them.

Common causes of freeze-ups include:

  • Dirty filters
  • Dirty evaporator coils
  • Low refrigerant levels
  • Closed-off supply registers

As it cools your home, your AC unit condenses water vapor into liquid that drains outside. When airflow is impeded by a dirty air filter or other obstruction, water ends up freezing on the evaporator coils before the condensed water can be drained away. The AC still runs, but doesn’t properly cool, and uses more electricity. Running your AC with ice on the coil can result in serious damage that requires repair or replacement of the compressor, the most expensive component in your system.

Thankfully, there are steps you can take to prevent AC freeze-ups.

If you see ice forming on the outdoor unit or pipes leading from the compressor, check your filters. Blocked or closed vents can also impede airflow, so make sure that yours are open and free of blockages.

Other common causes of freeze-ups include faulty fans that don’t circulate air through your ductwork, faulty thermostats, and low refrigerant levels. Low refrigerant levels make the coils too cold, preventing the system from absorbing enough heat, leading to a freeze-up. Since air conditioners do not burn refrigerant, low levels indicate a leak. Locating a leak is work for a licensed technician, who will likely need to recharge your refrigerant.

Cold weather is another cause of freeze-ups in certain regions. When nighttime temperatures drop below 60 degrees Fahrenheit, you should switch off your AC and open windows, or install an ambient temperature control, which allows air conditioners to operate properly in lower temperatures.

Annual maintenance tune-ups are your best defense against freeze-ups. These checkups should include cleaning both indoor and outdoor coils, checking and replacing air filters, a check of refrigerant levels, and a variety of other important elements of your system.

If your air conditioning system isn’t operating properly, or hasn’t been looked over by a professional recently, it’s time to call the experts at Gilmore. Our trained technicians will take all the steps necessary to ensure that your AC unit doesn’t experience a freeze-up or other breakdown when you need it most during the hot days ahead this summer.