What causes air conditioners to freeze?


Quick Answer

Common causes of freezing air conditioners are improper air flow, refrigeration issues and low outdoor temperatures. Ice can form on top of and inside of the air conditioner, which will keep it from operating properly.

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Full Answer

A lack of proper airflow within the unit is a common cause of frozen air conditioners. The lack of airflow causes the evaporator coil to freeze. Dirty air filters, impacted ducts and built-up dirt can all cause the coil to freeze.

Another common issue is either too low or leaking refrigerant. This causes the pressure to drop and the moisture in the air to freeze and collect on the coil.

A third common cause is outdoor temperatures lower than 60 degrees Fahrenheit. This is common, especially at night, as temperatures drop.

To repair a frozen air conditioner:

  1. Thaw it out
  2. Turn off the power to the air conditioner at the breaker box and allow the coils to thaw completely. Dry the coils, then turn the power back on and turn on the fan. Allow the fan to run to dry out the interior.

  3. Check the airflow
  4. Since airflow issues are common, first check for airflow issues by replacing the filter and cleaning any dirt or build-up.

  5. Add refrigerant
  6. If the freezing is caused by low refrigerant issues, either add more refrigerant or contact a professional for assistance.

  7. Turn off the unit
  8. During low temperatures, turn the air conditioner off to prevent freezing.

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