HELP! Why is my air conditioner frozen?

May 18, 2011

This unfortunate problem could happen to you. It’s especially bizarre when this incident occurs during hot summer days. For instance, you may notice your cooling system doesn’t feel like it’s working adequately, and when you go to check, find that your air conditioner unit is covered in ice. The cause of this freezing is the evaporator coil; the part of your air conditioner system that transfers (evaporates) heat from the inside to the outside of your home.

Below are several common problems that can cause your air conditioner to freeze up:

  • Inadequate Air Flow. Anything that restricts the air flow over the coil surfaces can disrupt the balance of your system and cause icing. Dirty filters, damaged blower motors and dirt build-up on the evaporator coil can all seriously obstruct air flow.

  • Insufficient Refrigerant. Refrigerant leaks or low levels of refrigerant can make the cold coil too cold and allow moisture in the air to freeze and accumulate.

  • Temperature. Faulty thermostats or thermostats that are set too low can cause an air conditioner to run constantly, which can eventually drop the temperature of the condenser below freezing. Also most outdoor units do not function well in temperatures below 60 F. If your nighttime temperatures are too low, the system will not operate properly and freeze-ups can occur.

What can you do if your air conditioner freezes up?

  • First, turn off your air conditioning system completely off and let it defrost.

  • Next, clean or replace any dirty filters and remove any visible dirt or obstructions.

  • Open all registers completely and make sure furniture or draperies are not blocking them.

  • Last, call an Air Conditioning Professional. Your system will need to be inspected to ensure there are no refrigerant leaks or damage to your equipment. NOTE: If you let the AC continue to run after the coil freezes up you are wasting money and risking damage to the compressor, the most expensive part of the air conditioner.

Regular maintenance on your air conditioning system helps you avoid many of these problems that can lead to a “frozen” system. During regular maintenance filters are cleaned or changed, thermostats are checked and leveled, refrigerant is checked for proper charge, and coils are inspected.


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Last Updated: June 07, 2024