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How to Fix a Frozen AC Unit

You want your air conditioning system to keep your house cool, of course, but what happens if a malfunction occurs and you're left with a frozen air conditioner?

Although, it may seem counter-intuitive for a system that’s used in the hottest weather to freeze, it can and does happen to many unprepared homeowners every year.  A frozen air conditioner can leave you and your household in an uncomfortable situation on a hot day.  Here’s how to tell if you have a frozen ac unit, how to prevent it and how to fix the problem:


Is My Air Conditioner Frozen? 

The first red flag signaling that your air conditioner has ice buildup may be that your system isn't reaching the desired thermostat setting. You may notice this more quickly in an upstairs area of your home. If your air conditioning system isn’t cooling your home properly, place your hand over one of the supply registers and feel the air coming out. If the air feels warm instead of cool, turn off the system and open or unscrew the access panel to the evaporator (check your manufacturer’s system diagram for the evaporator location). If you notice that you have frozen ac coils, or any of the equipment or panels are encased in ice, then your system’s refrigerant may have fallen below 32 degrees, resulting in a frozen a/c.

Related: When to Replace Your AC

What Do I Do If My Air Conditioning System Freezes? 

In many cases, you may be able to defrost the ac unit yourself.  You should avoid running the air conditioner if you think you have a frozen evaporator coil because this can place a strain on the compressor which could possibly cause damage and burn it out.  Find your electrical breaker box and turn off the switch that controls power to your air conditioner to start the thawing process on the coils, which could take up to 24 hours.  You can also simply, turn off the system and turn on the blower to help thaw the evaporator coils.  It’s best not to try to clear the ice by hand which could also damage components. Once the condenser and coils have thawed, remove any standing water that may have pooled around the equipment.


After the system is thawed, you’ll need to dry the coils.  If you haven’t yet turned on the system’s blower, restore power to the system if needed, and set the thermostat control to operate the blower or fan only.  This will help circulate air through the system and coils.  You may also be able to speed up the process with a hair dryer set on low heat.  Just take care not to use high heat or to get the hair dryer too close to the coils which could possibly crack them.

Related: Simple Fixes For Some Top Air Conditioner Problems 

How Do You Fix a Frozen Air Conditioner?

While a frozen air conditioner can be caused by different things and may require the expertise of a qualified HVAC technician to fix, there are some things that you can try yourself first.  

1. Examine the Vent Filters

Check the vent filters to see if they are clogged and restricting air flow.  Dirty filters can cause an air conditioning system to freeze. If they look dirty or discolored, change them and see if that fixes the problem.

2. Inspect the Coils and Fins

You can also inspect the coils and cooling fins around the evaporator to see if they need cleaning. If so, use a soft brush and gently remove any dust or debris.  Check to see if all the supply registers in your home are open in each room, too. Blocked registers may restrict air flow which can affect the evaporator temperature and cause problems.  

3. Check Coolant Levels

Low coolant can also affect your a/c system’s pressure and cooling efficiency, causing the unit to freeze.  To check on your system’s refrigerant levels and correct the levels, get a coolant installation kit at your home improvement store.  If you suspect that you have a refrigerant leak in your system, call an HVAC service professional.

4. Reset the Power

After you’ve taken steps to thaw and correct your frozen ac unit, run a test to see if it’s cooling properly again.  If you’ve shut the breaker off, restore power and turn the thermostat to the cool setting.  After a few minutes, you should be able to feel cool air blowing from the vents.  If the air is still warm or if the system cycles for a long time without reaching the desired thermostat setting, there may be additional damage to the unit or a refrigerant leak, and you’ll need to call a qualified HVAC technician for help.  

Related: Noises Your Air Makes and What They Might Mean

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How Can I Prevent a Frozen AC Line in the Future?

While a frozen ac may be caused by malfunctions or damaged equipment, proper maintenance can help avoid some issues.  Keep the evaporator coils clean, as dirty coils can restrict air flow across them.  Replace your system’s air filters regularly.  Most manufacturers suggest changing the filters every one to three months, but if you have pets, you may need to change them more frequently.  To remember to change your air filters, set reminders on your phone or computer, or link the air filter changes to other regular home maintenance chores. When you purchase filters, buy several at once so that you usually have extras on hand and can make the swap when you’re thinking about it. Keep air supply registers open for good air flow and circulation, and ask your HVAC professional to show you where your system’s refrigerant lines are located so you can check them regularly to make sure they aren’t blocked or bent. 

It’s also a good idea to keep trees and shrubbery trimmed away from outside equipment to help avoid branches, twigs and leaves from entering the system and causing problems. Consider having your HVAC equipment inspected and serviced each year by a qualified technician, who can help you properly maintain your system and may be able to troubleshoot potential problems. 

Remember, in addition to helping avoid problems like frozen systems, proper air conditioning system maintenance can also help your unit run more efficiently, which may help hold down your cooling costs. If you find that your system is in need of repair, remember that an American Home Shield home warranty could help protect your budget from costs associated with getting your unit back on track. 

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AHS assumes no responsibility, and specifically disclaims all liability, for your use of any and all information contained herein.

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