When an air conditioner sits unused for a long period of time, the moisture inside it can cause mold to grow. Mold in air conditioners is a common homeowner issue—one that’s important to tackle quickly. Some mold problems can be solved with a DIY cleaning job, but others will require professional remediation.

In this guide, we’ll explain how to clear the mold from your air conditioner. We also discuss the importance of proper AC maintenance, the dangers of ignoring a mold problem, and how to make sure your AC unit stays mold-free.

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Is Mold in AC Units Harmful?

In addition to smelling bad, moldy air conditioner units can cause a variety of health problems. Mold spores can become airborne and cause allergic reactions, asthma attacks, and other respiratory issues. In the worst-case scenario, these spores can also lead to serious long-term health problems, such as neurological disorders. People with weakened immune systems, such as those living with HIV/AIDS or undergoing chemotherapy, are especially at risk. 

Mold also affects your air conditioner’s efficiency. As mold accumulates, the unit must work harder to cool the same space and will use more energy in the process. This can significantly raise your utility bills.

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Signs Your AC Unit Has Mold

Mold is an unwelcome presence in any home. Unfortunately, it can easily start growing inside your air conditioner if the unit isn’t properly maintained. Here are some signs that your AC unit might be harboring mold:

• Visible signs of mold, such as black, brown, or green patches on the unit’s exterior
• An unpleasant musty smell coming from the vents
• Higher than normal energy bills
• Weak air flow coming from the vents
• Your AC unit running longer than usual
• Excessive condensation on the unit’s exterior 
• Warped or discolored ductwork 
• Allergy-like symptoms while the AC unit is running

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How To Check for Mold

If you suspect that your air conditioner may contain mold, turn it off or unplug it and inspect the unit. Look for visible signs of mold or mildew, such as dark spots, discolorations, or stains on the unit or its surroundings. Mildew may also appear as a powdery white or gray substance.

Focus your inspection on areas that are prone to moisture buildup, such as the evaporator coils, condensation pan, drain line, and blower compartment. For window or wall-mounted units, remove the grille and check the filter. Use a flashlight to inspect as much of the interior as you can. For a central AC unit, inspect the ducts, vents, fans, and exterior condenser unit.

Finally, use your nose. Take a few whiffs to detect any strong musty odors around your air conditioning unit that could indicate mold growth.

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How To Get Rid of Mold in Your AC Unit

Before you begin, gather your cleaning supplies as well as personal safety equipment. The Before you begin, gather your cleaning supplies as well as personal safety equipment. The Environmental Protection Agency recommends wearing gloves, unventilated eyewear, and a mask or respirator that covers your nose and mouth recommends wearing gloves, unventilated eyewear, and a mask or respirator that covers your nose and mouth.

• Step 1: If you have a window AC unit, turn it off and unplug it from the wall. If you’re dealing with a central AC system, you may want to flip the breaker for safety.
• Step 2: Use a screwdriver to take out any removable parts (such as filters) and check for mold growth. If found, put the affected parts in a plastic bag and properly dispose of them.
• Step 3: Clean out dust and debris with a vacuum cleaner.
• Step 4: Make a cleaning solution or use a commercially available mold cleaner. The EPA advises that bleach is often unnecessary and a mild dish detergent is preferable. However, if you want to use bleach, make sure to open windows and properly dilute it. Mix 1 cup of bleach into 1 gallon of water.
• Step 5: Soak a cloth in the cleaning solution. Use it to wipe down the unit’s inside, focusing on areas where mold might be present. Do not clean or rinse any of the unit’s electrical components 
• Step 6: Let the cleaning solution sit for 20 minutes before rinsing it off with clean water.
• Step 7: Allow the AC unit to air dry completely before reassembling it and turning it back on. This may take up to a full day

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When To Hire a Professional

Mold can be dangerous, and it’s important to handle it with caution. If the problem is extensive or returns after you’ve cleaned, consider hiring a mold remediation professional to remove it. They’ll have the correct tools, protective gear, and knowledge to safely and effectively remove the mold. An expert can inspect the unit for additional signs of mold that an untrained eye could miss.

A professional can also identify any other problems within the unit that might be causing mold, such as excess moisture or clogged drains. This allows them to provide a permanent solution, rather than a temporary fix.

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How To Prevent Mold Growth in Your AC Unit

You can take steps to prevent mold from occurring in the first place. Here are some tips.

• Clean or replace the filter every two months or according to the manufacturer’s instructions. The air filter is key to protecting your AC from dirt and debris. A dirty air filter can reduce your AC’s effectiveness and create an environment that’s conducive to mold growth. 
• Keep the area around your AC clean. Clear away any debris, dust, leaves, and other materials that can accumulate near your AC unit. This will help reduce the chances of mold spores entering the system.
• Regularly check your AC unit for water leaks and repair promptly if needed. Water in and around the AC unit is a major cause of mold. 
• Keep indoor humidity levels low. High humidity levels create an environment where mold can thrive. Use dehumidifiers to reduce indoor humidity levels and make sure your AC unit is properly ventilated.
• Turn the thermostat up instead of off. If you’re going on vacation for a few weeks, instead of turning the unit off, turn the thermostat up to 85 degrees or so. This way, it will still cycle occasionally, and air will still circulate through the unit.
• Have your AC serviced regularly. It’s important to have your AC serviced regularly by a professional HVAC technician. They’ll inspect your unit for mold and take measures to improve your indoor air quality.

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DIY vs. Professional AC Unit Mold Removal

Cost is typically the chief considerationwhen deciding whether to hire a professional for AC cleaning. A DIY approach is cheaper, as you’ll only pay for the supplies needed to complete the job. However, a professional will likely be more thorough.

Professional Mold Removal

Professional mold remediation has benefits. Professionals have access to specialized equipment and products that are designed for safety and efficiency. A professional can quickly identify the mold source and take steps to remove it, saving you time and trouble. However, this service is expensive: expect to pay $3,000–$10,000 for mold remediation depending on the severity of the problem.

Another factor to consider is feasibility. Removing visible mold from a window air conditioner isn’t complicated and requires no special equipment or knowledge. But a professional will do a better job if the mold is hard to access or spread throughout a larger HVAC system. Consider your safety when deciding between DIY and professional AC unit mold removal. Mold can cause health problems, so it’s best to leave the job to an expert if you’re not sure how to remove it safely.

DIY Mold Removal

Cleaning mold from your air conditioner can be tedious and difficult, but mild to moderate problems can usually be tackled on your own if you’re willing to take the time. 

If you opt for the DIY route, you’ll need some basic supplies such as safety eyewear, rubber gloves, a scrub brush, a vacuum cleaner, a mild detergent, a face mask, and a bucket of hot water. You may also need mold killer, depending on the severity.

The biggest disadvantage of this approach is that it can be time-consuming. There’s also no guarantee that it will completely eradicate all of the AC unit’s mold. If the problem persists after you’ve tried cleaning it yourself, hire a professional.

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Our Conclusion

Air conditioner mold can be harmful to your health if not quickly and effectively removed. You can prevent mold growth in your AC unit by keeping the air filter clean, repairing any leaking hoses or pipes, and identifying areas of excess moisture. 

If you find that your AC unit has mold, you can hire a professional for removal or attempt the job yourself. Professional mold removal is the preferred option for large units, since experts are trained to safely and permanently remove mold. DIY methods may not always be as effective. 

Regardless of your choice, you should take action as soon as possible to prevent the mold’s spread.

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FAQ About Removing Mold from an AC Unit

Is mold in AC harmful?

According to the Centers for Disease Control and Prevention, mold can cause respiratory problems, burning eyes, rash, and allergic reactions. People with asthma and those with compromised immune systems are likely to have the most severe reactions.

How can I prevent mold from growing in my AC?

You can prevent mold from growing in your AC by keeping all grates and air ducts clear and clean. This allows maximum airflow to all system parts. You should also replace air filters as needed. Clogged air filters attract mold and block the HVAC system’s air circulation.

Is it safe to run an air conditioner with mold?

If you suspect your air conditioner has mold, turn it off. Continuing to run it may spread mold spore throughout your ductwork and your home.

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