Troubleshooting a Frozen Evaporator Coil

An evaporator coil is the heart of the inside AC unit. This piece of equipment allows Freon gas to absorb heat from and dehumidify the return air system. The following is a brief explanation of how the evaporator coil works, the reasons why it freezes, how to fix it, and what to do to get your system working again.

How the Evaporator Coil Works

The evaporator coil in your air conditioning unit is responsible for absorbing heat. An air conditioner has three main components: a compressor, condenser, and evaporator coil.

The three components work together to convert the refrigerant from gas to liquid and back again. First, the compressor raises the pressure and temperature of the refrigerant gas and sends it to the condenser coil, where it is converted to a liquid. Then the refrigerant travels back indoors and enters the evaporator coil. Here the liquid refrigerant evaporates and cools the indoor coil.

A fan then blows indoor air across the cold evaporator coil, where the heat inside the home is absorbed into the refrigerant. The cooled air is then circulated throughout the home while the heated evaporated gas is sent back outside to the compressor. The heat is then released into the outdoor air as the refrigerant returns to a liquid state.

This cycle continues until your home has reached the desired temperature.

What Causes an Evaporator Coil to Freeze?

A frozen evaporator coil is an indication that something is wrong with your air conditioner. Most coils have their lives shortened by improper maintenance. What damages an evaporator coil is the lack of maintenance, low airflow, or low Freon levels.

Lack of maintenance – When you do not change or clean your air conditioner filter, you allow an excessive amount of dirt to be pulled through the filter by the blower suction power. This dirt is then lodged onto the air-conditioning coils.

A small amount of dirt can be generally washed away by the natural process of the evaporator coil removing humidity from the air in the form of condensation drain water. However, large amounts of dirt tend to lodge on the coil and accumulate to a point where it blocks the airflow that can pass through the coil.

Low airflow: Improper airflow is generally caused by a dirty filter or dirty coil and sometimes caused by an AC fan motor or wheel malfunction. Low airflow is also the cause of a frozen evaporator coil.

Low Freon level – a low Freon charge or a restricted freon line can also cause the evaporator coil to freeze up.

How to Thaw a Frozen Evaporator Coil

While many evaporator coil problems will require professional help, there are some things you can do on your own.

The first thing you should do is to let the coils thaw by turning the AC system off. Usually, it takes up to 24 hours to thaw on their own. You can also speed up the process by setting your AC thermostats to fan-only mode. This setting allows warm air to blow over the coils without the refrigerant cycle.

Don’t try to remove the ice yourself, as it could cause damage to the other components.

A frozen evaporator coil causes a lot of damage to your system. As ice builds on the evaporator coil, it forms a block of ice. This large piece of ice can do a tremendous amount of damage. As you know, ice expands; when this ice expands on and through the coil, it tends to cause freon leaks.

A good example of this would be to look at any road that you drive on. You’ll see where the city maintenance people have placed tar in the large cracks in the road. This is done to keep the winter water from going into the road cracks. But, unfortunately, that water in a road crack that freezes makes the crack even worse. This is the same thing that happens when the evaporator coil is freezing up.

A frozen evaporator coil is a common air conditioner problem. Not only can freeze-up situation, but damaged evaporator coil can also have disastrous effects on the compressor in your outdoor unit. If you’re stuck trying to figure out how to unfreeze your evaporator coil, then you may need professional help.

About Mas Broto

Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.