Why My Air Conditioner Freezes Up

Low Refrigerant

• Air conditioners use Freon or other refrigerants to cool the condenser coil so that air can flow across the coils, become cold, and then be forced into the house through the ducts. It seems logical that when the refrigerant gets low the coils would not cool so much, but this isn't the case. If the refrigerant is completely gone, it will not cool, but low refrigerant can actually make the coil get colder. The below-freezing temperatures that result will cause condensation that forms on the coil to freeze. More ice then will freeze on top of the existing ice until the coil is coated and system efficiency is hindered.

Restricted Airflow

• An air conditioner requires good airflow to work properly. When the air isn't pulling across the condenser coils fast enough, it can cause freezing at the condenser coil. During normal operation, the airflow is strong enough to remove the moisture from the area and prevent this freezing. The slower-moving air can make the temperature inside the unit drop and will make it retain more moisture, which leads to icing. Dirty air filters are the primary cause of this problem; replacing them regularly can improve airflow and prevent freeze up. Debris clogging the intake around your condenser unit can also cause the problem, so it should be kept clean and clear throughout the year.

Outdoor Temperatures

• When the outside temperatures drop, you probably don't use your air conditioner. But if you do, and if the outside air is below 60 degrees Fahrenheit, then you could experience a freeze up. Air conditioners are not designed to operate at temperatures below 60 degrees, and opening windows is a much better option. You will prevent icing problems, and you will save money by not running the air conditioner at a time when you don't really need it.

Oversized Unit

• If your air-conditioning unit is too powerful, cranking out more BTUs than is suitable for your home, then you could experience freezing in your air conditioner. Oversized air conditioners tend to leave too much moisture in the air and turn on and off too often. Most likely the air conditioner size is suitable for your home, but if it isn't, this could be a less common cause of freezing.