Home Cleaning The Professional’s Guide to Clearing Mildew Smell from Your AC

The Professional’s Guide to Clearing Mildew Smell from Your AC

By Albert G. Croley
3.7K views 1 min read

There’s nothing quite like turning on your air conditioner on a hot day—except when you’re greeted by a musty, mildew smell instead of cool, fresh air. Mildew odors coming from your air conditioner can make your home feel unpleasant, and they can even signal a deeper issue with mold growth or moisture buildup inside the unit. 

If you’ve been wondering how to remove mildew smell from air conditioner, don’t worry! With a few simple cleaning steps, you can eliminate the odor and ensure your AC is circulating fresh, clean air.

Why Does My Air Conditioner Smell Like Mildew?

The musty odor coming from your air conditioner is likely due to mildew or mold growing inside the unit. This happens when moisture accumulates in the system, creating an ideal environment for mold growth. 

Air conditioners, by nature, deal with a lot of moisture, especially in humid environments. If moisture isn’t properly drained or if filters and coils aren’t cleaned regularly, mold and mildew can build up, causing that unpleasant smell. 

Other potential causes include a clogged drainage line, dirty air filters, or mold growing on the evaporator coils.

Step-by-Step Process to Remove Mildew Smell from Air Conditioner

To remove mildew smell from your air conditioner, clean or replace the air filters, wipe down the coils with a mixture of water and vinegar, and ensure the drainage system is clear. Regular maintenance and proper ventilation can help prevent the smell from returning.

If your air conditioner is emitting a mildew smell, follow these steps to clean it thoroughly and get rid of the odor.

Step 1: Turn Off the Air Conditioner and Unplug It

Before you begin cleaning your air conditioner, it’s important to turn it off and unplug it from the power source for safety. This will prevent any electrical accidents and allow you to clean the unit without running the risk of damaging it.

  • Turn off the unit: Switch off the air conditioner at the thermostat or control panel. If it’s a window unit, unplug it completely.
  • Wait for the unit to cool: If the AC has been running, give it a few minutes to cool down before you start cleaning.

Once the unit is turned off, you’re ready to start cleaning and addressing the mildew smell.

Step 2: Remove and Clean or Replace the Air Filter

One of the most common causes of a mildew smell in your air conditioner is a dirty or clogged air filter. Air filters trap dust, dirt, and moisture, and if they’re not cleaned regularly, they can develop mold and mildew, which then spreads throughout the unit.

  • Locate the air filter: Depending on the type of AC you have, the air filter is usually located near the front of the unit or behind the grille. Check your unit’s manual if you’re unsure where it is.
  • Clean or replace the filter: If your air filter is reusable, clean it with warm, soapy water. Use a mild detergent to scrub away dirt, dust, and mildew. Rinse the filter thoroughly and allow it to dry completely before reinstalling it. If your unit uses a disposable filter, replace it with a new one.

Pro Tip: Regularly cleaning or replacing your air filter—ideally every 1-3 months—can help prevent mold buildup and improve the efficiency of your air conditioner.

Step 3: Clean the Evaporator Coils

Mildew can also form on your AC’s evaporator coils, where moisture naturally collects as the air cools. Cleaning these coils is essential to removing the mildew smell and keeping your unit running smoothly.

  • Access the evaporator coils: The evaporator coils are typically located behind the air filter. Once you remove the filter, you should be able to see the coils.
  • Clean with a vinegar solution: Mix equal parts white vinegar and water in a spray bottle. Vinegar is a natural disinfectant and deodorizer, making it ideal for removing mildew and mold. Spray the vinegar solution directly onto the evaporator coils, and let it sit for 10-15 minutes to break down any mildew buildup.
  • Wipe down the coils: After the vinegar solution has had time to work, use a soft cloth or a coil brush to gently wipe down the coils. Be careful not to damage the fins, as they are delicate and can bend easily.
  • Let the coils air dry: Once you’ve finished cleaning the coils, allow them to air dry completely before turning the air conditioner back on.

Cleaning the evaporator coils is a key step in eliminating mildew smells and ensuring your air conditioner runs efficiently.

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Step 4: Clean the Drainage System

If the water in your air conditioner isn’t draining properly, it can lead to mildew growth and that musty smell. A clogged drainage system can cause water to back up, creating a damp environment where mold thrives.

  • Check the drain pan: Most air conditioners have a drain pan that collects condensation before it’s drained away. Over time, dirt and mildew can accumulate in the drain pan, so it’s important to clean it regularly. Remove the drain pan, wash it with soap and water, and allow it to dry completely before putting it back in place.
  • Unclog the drain line: The drain line is responsible for carrying moisture out of the unit. If the line is clogged, it can cause water to back up and create a mildew smell. Use a wet/dry vacuum or a pipe cleaner to remove any blockages in the drain line.
  • Ensure proper drainage: Make sure the AC is properly leveled so that water can drain out efficiently. If the unit is tilted, water may pool inside, leading to mildew growth.

Keeping the drainage system clear and functioning properly will help prevent mildew and musty smells from returning.

Step 5: Disinfect the Vents and Grilles

The vents and grilles of your air conditioner can also trap dust, dirt, and moisture, which contribute to mildew growth. Cleaning these areas is crucial for eliminating the musty smell.

  • Remove the vents or grilles: If possible, remove the vents or grilles to access the interior areas of the unit where mold might be growing.
  • Clean with a vinegar solution: Spray the vinegar solution onto the vents and grilles, and use a soft brush or cloth to scrub away any dirt and mildew. Be sure to clean both sides of the vents to ensure that no mold is left behind.
  • Dry completely: After cleaning, allow the vents and grilles to air dry before reinstalling them.

Cleaning the vents and grilles will not only help remove the smell but also improve airflow and keep your air conditioner running efficiently.

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Step 6: Run the Fan to Dry the Unit

After thoroughly cleaning the air conditioner, it’s important to dry out any remaining moisture to prevent future mildew growth. Running the fan without the cooling function can help circulate air and dry the unit.

  • Turn on the fan-only setting: Most air conditioners have a fan-only setting, which allows you to run the fan without cooling the air. Turn on the fan for 20-30 minutes to dry out any remaining moisture in the unit.
  • Keep windows open: If possible, open windows in the room to help ventilate the space and remove any lingering mildew odors.

Running the fan regularly, especially after cleaning or on humid days, can help prevent moisture buildup and mildew growth in your air conditioner.

Step 7: Use Odor Absorbers

If you’ve cleaned your air conditioner but still notice a lingering mildew smell, natural odor absorbers like baking soda or activated charcoal can help.

  • Place odor absorbers near the air conditioner: Place bowls of baking soda or activated charcoal near the air conditioner to absorb any remaining odors. These natural deodorizers can help neutralize musty smells without the use of chemicals.
  • Use for a few days: Leave the odor absorbers in place for a few days to allow them to work. You can replace them as needed to keep the air smelling fresh.

Odor absorbers are a simple, chemical-free way to remove lingering mildew smells from your air conditioner.

Preventing Mildew Smell in the Future

Once you’ve successfully removed the mildew smell from your air conditioner, it’s important to take steps to prevent it from returning.

  • Clean the Air Filters Regularly: Regularly cleaning or replacing your air filters helps prevent dust, dirt, and moisture buildup that can lead to mildew growth.
  • Ensure Proper Drainage: Keep an eye on the drainage pan and line to ensure that moisture is being drained properly and not pooling inside the unit.
  • Run the Fan Regularly: Running the fan without the cooling function helps dry out the unit and prevent moisture buildup, which can lead to mildew growth.
  • Keep the Area Around the AC Unit Dry: Use a dehumidifier in humid rooms to keep the air dry and prevent excess moisture from affecting the air conditioner.

End Note

Dealing with a mildew smell from your air conditioner can be unpleasant, but with the right cleaning techniques, you can easily eliminate the odor and ensure your AC is circulating fresh, clean air. By cleaning the filters, coils, and drainage pipe regularly, and using natural odor absorbers like vinegar and baking soda, you’ll be able to get rid of the musty smell and keep your home feeling comfortable and fresh.

With proper maintenance and a little effort, you can prevent mildew from taking over your air conditioner, ensuring that you

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