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April 14, 2023

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    Few things are more frustrating than looking for refuge from the summer heat, stepping into your home, and finding that your AC is not cooling your living space. Several causes, including thermostat problems, clogged filters, and AC compressor or blower motor issues could be responsible for your AC not producing cold air. 

    HVAC maintenance can be challenging for even the most experienced DIYer. The top HVAC experts in your area can take the guesswork out of repairing your system. Learn more about how to diagnose these HVAC issues, then use the tool below to find a local pro.

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    7 Common Problems That Could Explain an AC Not Cooling

    There are seven main causes for your air conditioning system failing to blow cold air. These include:

    • Blocked or clogged condenser coils
    • Compressor issues
    • Dirty or clogged air filters
    • Duct problems
    • Electrical issues
    • Low refrigerant levels
    • Thermostat issues

    In the sections below, we’ll explain these AC problems, how to diagnose them, and how to fix the underlying issues.

    Blocked or Clogged Condenser Coils

    Condenser coils hold gaseous refrigerant and are located in your condenser unit outside. The condenser increases pressure on the refrigerant inside the coils, which causes it to condense into a gas. This chemical reaction releases heat, which is transferred to the exterior air through the copper condenser coils.

    Since they’re located outside, condenser coils can get caked in dirt and other debris, insulating the copper pipes and reducing how much heat they can transfer to the exterior air. Poor condenser coil performance results in the refrigerant remaining in gas form for longer and less heat being pumped outside. That leads to your AC blowing warm or hot air.

    To prevent your condenser coils from getting clogged or blocked, you should clean them twice a season — ideally, once in the spring and once in the fall. We recommend hiring a professional to carry out this process as part of your routine AC maintenance, as improper or incomplete cleaning may not fix your issue.

    Compressor Issues

    The compressor is part of the outdoor equipment that makes up your AC system. When heated refrigerant gets sent outside, the compressor uses pressure changes to condense the refrigerant back to a liquid. In the process, it uses fans to release the heat collected from your living space to the exterior of your home.

    If your compressor fails, hot refrigerant will make its way back into your home in a gaseous form. Since the gas cannot “boil” and absorb heat, air won’t be cooled. The result is your AC blowing hot or warm air.

    There are a few things you can look for to diagnose problems with your AC’s compressor, including the following:

    • Growling or grinding noises coming from your outdoor unit
    • Reduced airflow from your air conditioner
    • Warm air coming out of your AC

    Compressors are a critical part of your AC system, not only because they control cooling but also because problems can lead to electrical issues in your home, like blown circuits and an increased risk of electrical fire if your compressor is working overtime to try to cool your home.

    Compressors are complicated pieces of the AC puzzle, so professional maintenance or repair is required if you suspect an issue with your compressor.

    Dirty or Clogged Air Filters

    Another of the most common causes for your AC blowing warm air or failing to cool is poor airflow through your air filters. Your filters catch dust and debris — including pet hair, dander, and pollen — to prevent the recirculation of these contaminants in your indoor air. Over time, your air filters will naturally get clogged with debris, and clogging restricts airflow through them.

    Since your AC relies on cool air blowing into your living space, reduced airflow will cause less cool air to enter your home. The result is reduced cooling efficiency, which not only leaves your home warmer than you’d like but also puts added strain on your AC’s blower motor and other components.

    Clean or replace your AC’s air filters at the start of each cooling season and once leading into the heating season. Doing so will reduce airflow restrictions in your system, preventing undue stress on your equipment and increasing the cool-air flow into your home to maintain a comfortable temperature.

    Duct Problems

    A common reason for your AC failing to cool your home lies in the ductwork that travels behind your walls. The AC ducts carry cooled air from your indoor air conditioning unit throughout your home, so issues with your ducts can prevent that cool air from reaching your living space.

    There are a few problems you might experience that cause your ducts to deliver warm air to your home, including the following:

    • Air leaks: Over time, your air ducts, which are lightweight and somewhat fragile, can shake loose from vibration and continuous changes in temperature and humidity, especially along the seams. If you have leaks in your ducts, your cooled air will be lost to the space behind your walls or in your attic, which results in less cool air for your living space.
    • Blockages: Blockages in your ducts can restrict airflow, which means less of the cool air from your AC unit makes its way to your living space. This could be the issue if your AC is blowing moderately cool air. Partial blockages can result from animals that have crawled into your ducts and died, dirt and debris buildup, and faulty zone dampers.
    • Poor insulation: Ductwork should be insulated to prevent the cool air from heating up while traveling from your indoor unit to your living space. If the insulation breaks down, gets damaged by animals or age, or is installed improperly, you could feel insufficiently cool air coming from your AC.

    Problems with ductwork often involve getting behind your walls or into your attic and diagnosing problems using advanced equipment. It’s best to leave this work to professionals, especially since errors with DIY solutions can lead to additional cooling problems and decreased home energy efficiency. We recommend getting your ductwork checked by a professional at least once a year during your annual AC tune-up.

    Electrical Issues

    Some electrical issues could cause your AC to stop functioning correctly. Some signs that electrical problems are causing your AC not to blow cool air include the following:

    • High electric bills: If you notice that your energy bills increase unexpectedly, there could be a broader issue with your electrical system that leads to your AC malfunctioning. Electrical issues can cause problems with AC and thermostat communication, leaving your system running when it shouldn’t or slowing down its reaction to changes in temperature in your home. The result is a system that fights to keep up with demand and uses more energy to condition the air in your home.
    • Single breaker trip: It’s possible that an electrical surge caused your circuit to get tripped, which means your AC shuts down entirely. If your AC isn’t blowing any air, this could be the problem and is an easy fix.
    • Multiple breaker trips: If the electrical circuit for your AC system continues to get tripped without power outages occurring in your area, there’s likely an issue with the electrical components of your AC. If so, leave the breaker tripped and call a professional in for service. Trying to fix this problem yourself could leave you at risk of electrical shock and increase the likelihood of an electrical fire.

    Low Refrigerant Levels

    Refrigerant is a critical part of your AC system. Without sufficient refrigerant, your AC won’t cool your home. This chemical — usually Freon, also called R-22 — can easily convert from a liquid to a gas and back again. 

    When liquid refrigerant is delivered to your interior AC equipment, a pressure change causes it to boil and convert to a gas, a chemical process that pulls heat from the surrounding air. The result is cooled interior air.

    The refrigerant in gas form then gets pumped to your outdoor condenser, which, as the name implies, condenses the refrigerant back to liquid form. This process also involves a pressure change using fans blowing over the condenser coils. The condensation releases energy in the form of heat to the exterior air. The refrigerant is then pumped back inside to repeat the process.

     There are a few things that can cause issues with your refrigerant levels, including the following:

    • Improper installation: When your AC is installed, great care must be taken not to damage the refrigerant lines. Any issue during the installation — or even when your equipment is shipped or transported to your home — can lead to refrigerant problems.
    • Refrigerant leak: The pipes containing your refrigerant can become damaged over time from repeated use or trauma. If a pipe gets pinched or cracked, the refrigerant can leak into the atmosphere, leaving your AC unable to cool your home.

    Since refrigerant evaporates easily into the air, spotting a leak is difficult. Instead, you’ll need to look for frozen evaporator coils, a failing compressor motor, a noisy AC, and your AC blowing hot or room-temperature air.

    If you suspect your issue is with your refrigerant, you’ll need an expert to address the problem for you. They have special equipment to detect refrigerant leaks and refill the refrigerant, so contact a professional immediately if you suspect this is the reason your AC is not cooling your home.

    Thermostat Issues

    Your thermostat is the portion of your heating and cooling system that measures the temperature in your living space and tells your heating or cooling equipment to turn on and off. When the thermostat is set to “cool,” it will turn on your AC when your interior temperature gets above a certain temperature and shut it off once it reaches the target temperature or slightly below it.

    Issues with your thermostat could be the culprit behind your AC failing to cool your home. If the thermostat isn’t properly activating your HVAC system when the temperature exceeds the desired range, your AC won’t turn on to begin cooling.

    There are a few issues that you could be having with your thermostat. These include the following:

    • Battery failure: Most thermostats are hardwired into your home but also have backup batteries to save your heating and cooling preferences in the event of a power outage. If your battery dies and you experience a blackout, your preset temperatures could be lost and reset to higher than you’d like. The result could be that your thermostat fails to trigger your AC to turn on.
    • Calibration issues: Your thermostat relies on a thermistor, which measures electrical resistance changes based on the temperature in the room, to detect temperature. You could get inaccurate room temperature readings if the thermistor isn’t calibrated properly. If those readings are too low, your thermostat won’t trigger your AC to turn on to start cooling.
    • Poor thermostat placement: Many thermostats only have thermistors inside, which means the temperature where your thermostat is located provides the only reading to trigger your AC to come on. If your thermostat is in an area that’s near your AC or in a naturally cool area of your home, it won’t trigger your AC to come on as often as it should to keep the rest of your house comfortable.

    Since your thermostat is a critical part of your AC system, you should perform routine maintenance and battery replacements to keep it in good working order. Since thermostat repairs can be the most cost-effective solution for your AC not cooling your home, we recommend you check it first for issues if your AC isn’t working.

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    AC Maintenance Tips

    Problems with your AC blowing hot air can be frustrating, especially since the solutions can be expensive. It’s much more cost-effective to carry out routine maintenance than it is to wait for a serious problem to occur and then pay for a repair. 

    Routine maintenance on your system ensures that your living space remains cool and comfortable. It also helps improve your home’s energy efficiency, reducing energy bills, saving you money over time, and reducing the strain on the environment. Preventative maintenance will also keep your system running and help avoid outages.

    Below are some things you can do in the way of routine maintenance to keep your AC running properly:

    • Clean ducts regularly: Routine duct cleaning at least once yearly will reduce stress on your system, help avoid outages, and keep the air circulating in your home as clean as possible.
    • Get a professional tune-up: A tune-up once a year on your AC system can help avoid issues like failing to cool, cut down on repair costs, and extend your system’s life. A tune-up includes proper cleaning, duct inspections, and lubricating moving parts to keep your system in tip-top shape.
    • Get regular inspections: Your AC has many moving parts, and at least one annual inspection can ensure nothing is at risk of breaking down. It’s cheaper to service a functional component and avoid breakage than to replace an already damaged component.
    • Make periodic replacements: Since your AC works overtime in hot temperatures to cool your home, parts will eventually need to be replaced to maintain proper functionality. Replacing dirty air filters, belts, and other components that break down over time is an easy way to avoid cooling loss in your home.
    • Replace filters: One of the easiest things you can do to cut down on AC maintenance costs and issues with cooling is to replace your filters at least twice a year, once in the spring and once in the fall. You can do this for very little money, which will help you avoid much more costly problems resulting from air restriction and damaged fan motors.

    Final Thoughts About AC Not Cooling

    If you find that your AC isn’t cooling your home, we strongly recommend hiring a professional to carry out a system diagnosis and any necessary repairs. Air conditioners are complicated, and, as you can see from the issues we’ve mentioned above, a lot can go wrong that can lead to a similar set of symptoms.

    If your AC isn’t cooling your living space or is blowing hot air, it’s best to have an HVAC technician look at your system, troubleshoot the problem, and carry out a solution for a permanent fix. Additionally, having a pro do routine maintenance on your system at least once a year will significantly reduce AC repair costs and outages and will help improve your home’s energy efficiency.

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    FAQs About Air Conditioners Not Cooling

    How often should I clean my AC filters?

    Plan on cleaning or replacing your AC filters at least twice a year. The optimal schedule for doing so is once at the beginning of the cooling season and then once before you switch your system to heat.

    What is the average lifespan of an AC unit?

    The typical central air conditioning system is expected to last between 15 and 20 years, although some systems experience major issues before this timeframe, and others last for many years beyond it. One of the easiest and most affordable ways to extend the life of your system is to have tune-ups and preventative maintenance done at least once per year and get issues addressed as quickly as possible.

    What should I do if my AC thermostat is not working properly?

    Issues with your AC thermostat can stem from various problems, including a loss of presets due to a power outage and battery failure, calibration issues with the thermistor, or poor placement of the thermostat, which causes inaccurate indoor temperature readings.

    First, you can confirm that you have power in your home and check to see if your preferred thermostat settings got wiped out from a blackout. If they did, replace the battery and redo your presets. Next, you should check to ensure your thermostat is set to “cool.” This simple issue can stem from forgetting to switch from “heat” to “cool” at the turn of the season.

    If neither of these is the issue, we strongly recommend having a professional HVAC tech assess your system. Other problems can include electrical issues or problems with other AC components, which are complicated and potentially dangerous to fix yourself.

    What are the signs of low refrigerant levels in my AC?

    If your AC has low refrigerant, you will likely notice your unit blowing room temperature or hot air. You may also notice your energy bills spike as your unit tries to keep up with the demand for cooling without refrigerant. You may also notice a hissing noise coming from your outdoor unit, ice forming on the evaporator lines on your indoor unit, or your AC continuously running to try to keep up with demand.

    If you experience any of these problems, we recommend having an HVAC professional assess the issue, refill the refrigerant, and fix the leak to prevent recurring problems.

    Editorial Contributors
    Dan Simms

    Dan Simms


    Dan Simms worked in real estate management for five years before using his experience to help property owners maintain their own homes. He got his master’s degree in English Literature and Creative Writing, and he now enjoys sharing his knowledge about homeownership and DIY projects with others on Today’s Homeowner. When he’s not writing, he’s usually outdoors with his wife and his dog, enjoying mountain biking, skiing, and hiking.

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    Roxanne Downer


    Roxanne Downer is a commerce editor at Today’s Homeowner, where she tackles everything from foundation repair to solar panel installation. She brings more than 15 years of writing and editing experience to bear in her meticulous approach to ensuring accurate, up-to-date, and engaging content. She’s previously edited for outlets including MSN, Architectural Digest, and Better Homes & Gardens. An alumna of the University of Pennsylvania, Roxanne is now an Oklahoma homeowner, DIY enthusiast, and the proud parent of a playful pug.

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