Why Do AC Coils Freeze Up?

When AC coils freeze up, it may be due to a lack of airflow, improper draining, or a refrigerant leak. AC coils, also called evaporator coils, are among the main components of your AC unit. As warm air passes over them, the coils remove the heat and humidity and your AC system distributes cooler air into your home. When heating your space, the coils create heat which your blower fan can send out.

The coils work alongside the condenser, which condenses the humidity into water for elimination. If there is no humidity in the air for the coils to remove, or if the airflow is obstructed, ice can develop in your unit. AC coils can freeze at any time of the year, so be sure to check and maintain your system regularly.

Common Causes of a Frozen Evaporator Coil

A variety of issues can cause your evaporator coil to freeze over. These could be problems stemming from within your AC system or outside, including:

Dirty evaporator coils

Evaporator coils can collect dirt and debris over time, hampering the heat exchange process. Dirty coils can’t absorb heat from the air, so the condensation becomes too cold and freezes up.

Dirty air filter

A dirty air filter prevents the coils from absorbing enough heat from the air to function properly. It can also spread dirt and congest other parts of your AC system, including the evaporator coils.

Low refrigerant

Low refrigerant makes your AC system overwork, which can cause the coils to freeze up. In this case, you may have a leak or insufficient charge.

Clogged drain pipe

Condensation on the evaporator coils is a natural part of how the coils work. If the drainpipe is clogged or malfunctioning, too much condensation can form and freeze.

Low outdoor temperature

If the outside temperature is too low, your system will have no heat from the air to absorb. This can make the condensation on the evaporator coils freeze up.

How Do I Fix a Frozen Evaporator Coil?

Having your AC system professionally inspected and serviced is the best way to find and fix what’s making your coil freeze over. Your unit may have instructions for de-icing, or you can try some safe methods such as these:

Thaw the coils

Turn off your AC or turn the system to “fan-only” for up to 24 hours. If your system has a heat pump, turn it on defrost mode.

Check the air filter

Make sure your air filter is new and clean. Replace if needed so that the air can flow properly.

Clean your coils

The easiest way to take care of your evaporator coils is to let an expert handle the cleaning. If you prefer to DIY, though, you can follow these steps to clean the coils yourself:

  1. Turn off your AC system at the panel and breaker.
  2. Find the coils near the blower fan in the air handler.
  3. Spray coil cleaner or a solution of household cleaning detergent and warm water on the coils.
  4. Let the solution sit for 10 minutes, then wipe away the grime with a soft cloth.

If none of these steps work, call a professional AC service to inspect your unit.

How Do I Prevent AC Coils From Freezing?

Preventive maintenance is the best way to help keep your AC coils from freezing. Check and change your air filters every 60-90 days. Have a professional HVAC technician inspect and tune-up your AC unit at least once a year. Let an expert check your system before the summer months when you’re likely to be using your AC more. This helps ensure that your AC continues to work efficiently and keeps you comfortable.