What Causes an Air Conditioner to Freeze Up?

When it comes to air conditioning units, most people assume colder is always better. However, sometimes, certain parts of your system can get too cold to function. If you have ice building up inside your AC unit, it can end up blowing hot air or breaking down altogether. To solve this problem, you need to understand why it is happening in the first place.

What It Means When an AC Freezes

When an air conditioner freezes, ice starts to build up around the evaporator coils. Evaporator coils hold chilled refrigerant. As air from your conditioner moves over these coils, the refrigerant absorbs heat from the warm air and sends it outside to be dispelled. However, when airflow is not moving over the coils properly, ice can start to build up. It may take a while for you to notice the problem.

Often, the first sign is that air blowing out of your registers feels warm, no matter how low your thermostat is set. In some cases, your coils may freeze and thaw over and over. When this happens, you may notice pools of water puddling around the AC unit.

You can check for a frozen coil by opening up the part of your system located inside your house. There might be a fine layer of frost on the coils, or there could be a huge chunk of ice all the way around the interior. If you do not catch any of these signs of a frozen coil, your air conditioner may eventually break. At this stage, signs of a frozen coil will be an AC system that does not turn on.

Ice Buildup Caused by Low Refrigerant

One of the most common problems that leads to a frozen air conditioner is low refrigerant levels. When you do not have enough refrigerant in your coils, pressure starts to drop. Instead of condensation passing outside, it lingers around the coils. This causes moist, warm air to condense on the coils and start to freeze.

Even a thin layer of frost will keep your coils from working properly, so the ice buildup will just get worse and worse. Refrigerant is meant to stay in your AC system for years, which means low refrigerant is typically a sign that there is a leak. It can be dangerous to handle these chemicals yourself, so you need someone fully licensed in working with refrigerants.

Freezing Due to Poor Airflow

Any time air is moving too slowly over your evaporator coils, ice can start to form. This issue happens because your air conditioner is not getting enough warm air. As temperatures start to drop, condensation freezes and your air conditioner stops working. There are all sorts of issues that can impair airflow.

In many homes, poor airflow is just caused by a dirty filter clogged with hair and dust. Airflow can also be impeded by blocked ducts, closed grates, or closed dampers. Walk around your house and check each air vent. If you feel air leaking from the side of the grate, this might be the cause of your frozen AC unit.

Frozen Coils Caused by Dirty Coils

Evaporator coils have to carefully balance heat and humidity to work correctly. If your evaporator coils get dirty, they may not absorb water fast enough to move it away from the coils. This water then becomes super chilled until it eventually freezes. When coils are dirty, you often end up with particularly big chunks of ice since the drip pan may become clogged as well.

Dirty coils are entirely preventable. You can do a lot to keep the interior components of your AC system clean just by switching out your filters regularly. It is also a good idea to schedule annual maintenance for your air conditioner. During a maintenance appointment, the technician will use special cleaners to remove any dust before it can start impeding the evaporator coil function.

Ice Buildup Due to a Damaged Blower Fan

Since any sort of slower airflow can lead to freezing in your air conditioner, the blower fan plays a very important role. This fan helps to push air up into your system, move hot air outside, and blow cool air through your vents. It is possible for a blower fan to break, leading to ice all over your coils.

Sometimes, the issue is as small as a slightly bent blade that slows down the fan. Other times, it may be due to belts snapping or other parts breaking down. A broken blower fan is usually easy to identify since you will notice significantly less air moving through your system. Depending on the cause of the breakage, a blower fan can be very easy or very challenging to fix.

Frozen Coils Caused by a Faulty Thermostat

Often, the problem causing your frozen air conditioner has nothing to with your AC unit itself. In some cases, the issue is the thermostat. When a thermostat breaks, it may improperly register indoor temperatures, or it may fail to actually control the cooling system. This can lead to your air conditioning unit running nonstop. Though AC units are meant to run for long periods of time, they do need breaks occasionally.

When your AC unit keeps running and running, the temperature in the system can get too cold. Without warm air moving over your coil, it ends up freezing. To test and see if a frozen coil is caused by a broken thermostat, check your thermostat to see if the temperature displayed is inaccurate. Then, try moving the temperature to its lowest setting. If the AC unit still does not shut off, the problem causing your frozen air conditioner might be the thermostat. In some cases, your thermostat just needs to be reset. In others, you may need to replace it.

What to Do If Your AC Freezes Up

If you notice frost forming on your air conditioning system, the first thing you should do is turn off the unit. If you run your air conditioner with frozen coils, it will have to keep working harder and harder. This can eventually cause damage to your compressor, which is very expensive and difficult to fix. After you shut off the system, you can use a hairdryer or other form of gentle heat to melt the ice, and then turn your system on again.

However, your air conditioner will keep freezing until the underlying problem is addressed. Some issues, like dirty coils, are things you can fix yourself. However, for more complicated problems like a broken fan, you should get help from a professional. The right repair will keep frozen coils from happening again.

If your AC unit keeps freezing up, we can help to identify and solve the underlying problem. At Christian Brothers AC, Plumbing & Electrical, we assist customers with all sorts of repairs, installations, and maintenance services in Phoenix. Our highly experienced technicians work on a variety of plumbing, heating, cooling, and electrical systems. Learn more about our services by giving us a call today.