If your air conditioner seems less effective than usual, or perhaps your house is uncomfortably cold even during the heat of summer, then your air conditioner might be frozen. Take a look at your unit and see if you notice ice on any of the external components or if the interior is dripping wet.

Here are some definite indicators that your AC unit is frozen:

  • The copper piping is coated with a thick layer of ice.
  • The filter is soaked.
  • The evaporator coil is a solid block of ice.

Why Does an Air Conditioner Freeze?

Your Filter is Dirty

A dirty filter is a common cause of a frozen air conditioner. Your AC needs adequate airflow to run properly and this is impeded when the filter is dirty. When this happens, you need to clean or replace it. If your filter is dirty it can cause other problems, as it makes your unit work harder than it needs to and affects the quality of air in your house. Filters should be changed at least once a month and regular maintenance of your unit is necessary to keep it running properly.

It’s Too Cold for the AC

When the seasons change, particularly on cool nights during late summer or autumn, your air conditioner is more likely to freeze. The AC needs to cool the air to 18-20 degrees less than you want your house temperature to feel. If it’s cold at night and your thermostat is low, your air conditioner might be frozen by morning.

You Have Low Freon Levels

Believe it or not, low refrigerant levels cause your AC unit to ice up. Without enough refrigerant in the system, the evaporator coil inside your AC gets too cold and as condensation forms, the cold evaporator coil turns this condensation into ice. That’s why one of the main signifiers of a frozen AC unit is an evaporator coil that’s turned into ice. Low Freon levels can be fixed with a recharge sometimes, but they often indicate a bigger problem. This is a dangerous chemical, so make sure you contact a professional to replace low refrigerant levels.

The Vents are Blocked

Blocked vents restrict the airflow to the evaporator coil, which causes freezing. Just as with a dirty filter, any vent obstruction will affect proper air circulation. Cold air may also concentrate in one particular area and cause ice to form.

Your AC Unit is Old

HVAC systems have a limited lifespan and lose efficiency as they age. If your unit is ten years old and is experiencing frequent freezing, it’s time to look for a replacement.