Why does my AC unit have ice on it?

Ice on your air conditioning unit often happens because of low refrigerant charge, or because air is not flowing properly through the system. If you have ice on your air conditioner, shut the unit off and allow it to defrost. This is required to troubleshoot the problem. Call us for service.


A frozen AC unit can dramatically reduce efficiency, which can cause the AC to work much harder to cool your home. You may notice this if the unit is running a lot, but not cooling well. A frozen AC can also cause the system to not work at all. ACs can freeze during the hottest summer months. Below are 5 causes and possible solutions to when you see ice on your AC unit.

  • Low Refrigerant
    • If your refrigerant (AKA freon or R-22) is low, you may have a leak. Low refrigerant lowers the pressure in the system, which also causes lower temperatures. This can cause ice to form on the AC’s evaporator coil inside, as well as the suction line outside.
    • Solution: Have a qualified HVAC technician repair the leak and recharge the coolant. Air conditioners are closed systems, so you should never run low on refrigerant unless there is a leak. It is imperative you fix the leak, rather than just refilling the system. Sometimes it is better to replace an older system.
    • Prevention: Have your air conditioner inspected and serviced every spring to catch potential problems and make sure it has the right amount of refrigerant.
  • Dirty Evaporator Coil
    • A dirty evaporator coil can cause ice to form on your air conditioner because it restricts airflow through the unit. A dirty coil can also make the AC use more electricity, causing damage to the compressor.
    • Solution: To prevent your cooling system from breaking down, shut the unit off until the coil is cleaned or replaced.
    • Prevention: Clean the evaporator coil regularly.
  • Mechanical Failure
    • A damaged fan or kinked refrigerant lines can cause your central cooling system to freeze up.
    • Solution: Have a licensed HVAC professional inspect and repair the unit.
    • Prevention: Regular maintenance of your heating and cooling systems, generally in spring and fall, will reduce the risk of these issues.
  • Restricted Airflow through the AC unit
    • In order to function properly, air conditioners rely on air flowing through the system. Too little airflow causes the AC unit to freeze up. Airflow can be restricted by dirty air filters, closed vents, clogs or leaks in the ductwork, or something blocking the outdoor unit.
    • Solution: Depending on what’s restricting the airflow, you may need to change your air filter, clean your ductwork or repair your air ducts. You may need to also clean your outdoor AC unit.
    • Prevention: Change the air filter once a month during heavy-use times. Opening your vents and cleaning your outdoor AC unit can also help.
  • Outside Temperature is too Cold
    • Air conditioners weren’t designed to be used when the outdoor temperature is below 62 degrees Farenheit.
    • Solution: Turn off the AC unit to allow it to thaw.
    • Prevention: Turn off the air conditioner at night when the temperature is predicted to be in the low 60s or lower.
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