What Can I Do When My AC Unit Freezes Up?

July 19, 2022
Frozen AC in Seattle, WA

You may be surprised to see your AC unit freeze up. Can it really do that in the heat of the summer? It happens more frequently than one would think. You can do something about the situation. It’s important to find out why your AC unit froze up so you can prevent it from happening again.

Thaw It Out

If you see your AC unit frozen over, the first step is to turn the unit off at the electrical breaker box. You then need to let the ice thaw. It can take up to 24 hours for it to thaw out completely. You may want to leave your home while this happens, as your home is uncomfortably warm. However, check the forecast and make sure your pets will be ok.

If you can’t leave your home, go to the thermostat and change the fan setting from “auto” to “on.” This will keep air circulating through your home. Turn on any fans you have. You need to avoid turning on your AC unit, as this can damage the AC compressor. This part is very expensive, so you may end up with a really large repair bill if you do turn on the AC.

You may have heard from others that you can chip away at the ice with a hammer, screwdriver or other tool. This is a huge mistake that can cost you a lot of money, as it’s easy to damage parts of the indoor AC unit when you do this. It’s definitely best to let it thaw out naturally.

Dry the Evaporator Coils

Once the evaporator coils are dry, it’s time to dry them off. Flip the breaker to restore power to your AC system. You next need to change the settings on your thermostat, so only the fan will run. This will cause air to circulate through the evaporator coils and dry them out.

You may now be able to use your AC system as normal. However, you need to find out why your AC unit froze up to prevent it from happening again. Not only is it inconvenient to deal with this situation, but it can damage other parts of your AC system.

Dirty Air Filter

A dirty air filter is the top reason why your AC unit froze up. The air filter cleans the air that passes through it. Over time, it traps air pollutants like dust, dirt, pollen and pet dander. As it gets dirtier, it impedes the flow of air. It can even become clogged and prevent all air from flowing through it. A lack of airflow will cause your AC unit to freeze over.

You should check the air filters every month. Change them when you can see they’re dirty, which is somewhere between one and three months. There are several factors that affect how often you change the filters. These factors are the type of air filters you have, the square footage of your home and the amount of pollen in your area.

Homes that have smokers need the air filters changed often, as do homes with people who have allergies, asthma and heart diseases. How often you use your AC system will also affect how often the air filters need to be changed.

Low Refrigerant

Low refrigerant levels can cause your AC unit to freeze over. There are signs of this problem. Your AC system may be blowing hot air, or it has long cooling cycles. The air inside your home is humid, or you hear a bubbling or hissing sound. Another sign is that you have unusually high utility bills.

This problem can only be solved by an HVAC company. The technician will use tools to check the refrigerant level in your AC system. If they determine it’s low on refrigerant, they’ll first find the leak and fix it. They’ll then recharge your system with new refrigerant.

If you have an AC unit that’s over a decade old, it probably has R22 Freon as its refrigerant. This type of refrigerant was discontinued as of January 1, 2020, because of the damage it causes to the ozone layer. While you may be able to have the refrigerant charged, it will be very expensive to do so.

Airflow Problem

A lack of proper airflow can cause many issues, among them your AC unit freezing up. A common reason for this problem is people have closed or blocked vent returns and registers. While some people think closing vents in little used rooms saves money, it doesn’t in either the short or long term.

Inadequate airflow makes your AC system work much harder than it should. Your AC unit was installed to cool your entire home, not just part of it. Make sure all the registers in your home are open and that nothing is obstructing them such as a rug, drape or furniture.

Poorly designed or installed ductwork may also cause airflow issues. Sometimes a home has the wrong size of ducts. Additionally, ducts can be damaged by pests and birds. When your ducts are damaged, air doesn’t properly circulate through your home. You can fix ductwork that you can see with mastic, tape and insulation. For the rest, you’ll need to have an HVAC company do this work.

Dirty Evaporator Coils

Over time, the evaporator coils in your indoor AC unit will collect dust, dirt, hair and other air pollutants. The evaporator coils remove humidity from your home, with the resulting moisture dripping into a pan and then leaving your home through a condensate drain line. This process can result in the drain line becoming clogged with whatever collected on the evaporator coils.

When the condensate drain line gets clogged, it backs up water into the evaporator coils. This water will cause the coils to freeze up. You can help prevent this by pouring a 1/4 cup of distilled white vinegar into the drain line every month. When you schedule preventative AC maintenance, the technician will also check the drain line to make sure it’s clean.

Broken Fan Motor

One major reason that the AC unit will freeze is when the outside fan motor can no longer blow the cool, compressed air into the unit. This will require replacement by a professional.

Schedule Preventative AC Maintenance

You should schedule having your AC unit professionally maintained every year. You should schedule this in the spring when HVAC companies tend to not be overly busy with repairs and installations. The technician will inspect your entire AC system to see if everything is working as it should. They’ll clean critical components, lubricate motors, check electrical connections and more. Preventative AC maintenance goes a long way toward preventing AC units from freezing up.

Brennan Heating & Air Conditioning is a locally owned and operated company that repairs, replaces and maintains air conditioners and heaters. Our company performs air duct cleaning and free energy consultations. We install and repair water heaters. If you need electrical services, rely on us for panel change-outs, home electrical inspections, circuit upgrades, maintenance and repair, breaker/fuse replacements and more. Our NATE-certified technicians can work on all makes and models of AC systems. Please call us today to find out more.

Brennan Heating & Cooling icon