Black Mold on Evaporator AC Coils? (How To Clean It Off)

Evaporator coils are the part of your AC unit that absorbs heat from incoming air. The refrigerant inside the coils cools down the indoor air, causing condensation on the outside. This condensation falls into a drain pan that leads it away from the AC.

But, all of the moisture doesn’t always drain away, making parts of the AC vulnerable to mold growth. The evaporator coil is one of them. Below, discover how mold grows on the evaporator coils and how to get rid of it.

AC Evaporator Coil: How Does Black Mold Grow Here?

Black mold is a type of fungus that feeds on organic materials commonly found in household materials. Mold spores are naturally found in the air around us. They don’t grow unless they have access to three things: moisture, food, and darkness.

Dust and dirt that go through an air conditioner are an excellent food source to the fungus, while the condensation from the cooling process provides moisture. It’s dark inside the air conditioner, which seals the deal.

It’s easier for mold to grow on evaporator coils when other parts such as the air filters and the drain line are not working correctly. The filters are responsible for filtering dust and debris from the air. If they fall short, this dirt gathers inside the AC, providing a breeding ground for mold.

The drain line should lead away from the water that collects at the bottom of the unit from the cooling process. If it’s clogged or faulty in any way, the water accumulates, creating the damp conditions necessary for fungus to grow.

Signs of Black Mold in Your Air Conditioner Evaporator Coil

It’s easier to tell when there’s mold in AC coils if you know the signs to look for. Here are four common signs you should beware of to allow you to tackle the mold problem before it gets serious:

Musty Smell Indoors

When there’s black mold on AC coils, its smell will come through the air ducts. The fungus has a musty smell, and it will spread indoors as a result. Beware that you might be insensitive to the smell because you’re used to the house, but a visitor might notice it immediately.

Distinct Odor Increases When AC Is Running

If the musty smell increases when the AC is running, it’s another indication that you’ve got mold in the AC. The odor increases in this case because of the increased airflow, which brings in more of the spores—and the mold’s smell—indoors. This odor will keep getting stronger until you remove the mold.

Respiratory Irritation When AC Is On

Molds spores are allergens that disturb the respiratory tract. If you or other inhabitants of your house start sneezing, coughing, or getting watery eyes once the air conditioner is turned on, it’s a sign that you’ve got mold spores coming through the air ducts. These spores can cause adverse reactions on people with existing respiratory conditions and cause healthy ones to develop respiratory infections.

Patches Around The Evaporator Coils

Black mold grows in slightly furry patches that are dark in color. After noticing the above signs, check the coils for dark brown, dark green, or black patches. They can also have an orange shade with white flecks. This is your final confirmation that you have a mold problem you need to address.

Signs of Black Mold

Best Way to Clean Black Mold In Your AC Evaporator Coil

Once you’ve established that there’s mold on your AC’s evaporator coils, it’s time to clean them. Fortunately, cleaning mold from evaporator coil is a simple process that doesn’t require special skills or equipment. Plus, the cleaning agents are easy to find.

To remove mold from AC evaporator coils, you’ll need the following items:

  • Latex gloves
  • Dust mask
  • Goggles
  • Screwdriver
  • Clothes that cover your arms and legs
  • AC coil mold cleaner

The clothes and gloves are necessary to protect your skin from the spores, which can cause a rash or itching if you come into contact with them. The dust mask keeps you from inhaling the spores, which leads to respiratory tract irritation, bringing along allergic reactions. You’ll need the goggles to protect your eyes from the fungus and the cleaning product.

Once you have everything ready, here’s how to clean mold off evaporator coils step by step:

  1. Turn off the power to the air conditioner or unplug it.
  2. Using the screwdriver, open the evaporator coil access panel. Check the manual to find where the coils are located and the best way to reach them.
  3. Shake the cleanser can and spray the product on the area on the coil with the mold. Ensure to cover the fungus with the foam.
  4. Leave the product to set in for as long as indicated on the instructions.
  5. While the product sets in, clean the drip tray by scraping off any debris.
  6. Wipe the coils clean with water.
  7. Flush the drain line with hot water to get rid of the cleanup residue.
  8. Put back the access panel.
  9. Turn on the air conditioner.
Anti Mold Spray Bottles

How to Prevent Black Mold Growth in Your AC’s Evaporator Coil

The best way to prevent black mold in evaporator coils is by stopping the build-up of dirt and moisture in the system. To achieve this, ensure all parts of the air conditioner are working optimally, especially the air filters and the drain line.

Do this by regularly checking, cleaning, and replacing the filters when necessary. Clean the drain line frequently to prevent clogging to allow quick and total drainage of condensed water.

Another way to prevent black mold on the evaporator coil is by installing a UV light on the indoor air handler. UV light kills mold spores, so it’s perfect for keeping the fungus from growing.

People Also Ask (FAQ)

What does black mold smell like?

Black mold has an earthy, musty smell—much like a mix of dirt and rotting leaves.

Will black mold stop the AC from running?

Black mold on the AC coil will not stop the unit from running. Instead, it’ll keep circulating in the AC and into your house, ruining air quality and exposing you and your family to harmful spores.

What kills black mold naturally?

Black mold will stop growing in the absence of moisture, darkness, and food. But, it doesn’t die on its own. Instead, it remains inactive and thrives again in the presence of moisture. Therefore, the only way to kill mold is by getting rid of it with disinfecting agents. Natural options include white vinegar and baking soda.

Can mold build up on my evaporator coils?

If black mold is left untreated, it keeps growing and builds up on your evaporator coils. With time, bubbles of mold on AC evaporator coils end up in the house. Even if they don’t find a damp, dark place to grow, their presence in the air increases your family’s risk of developing respiratory infections.


Never let a mold problem on your AC evaporator coils fester. Mold undermines your AC’s air-cleansing ability and endangers your family’s health. If you have any questions about how to clean mold from air conditioner coils, consult an HVAC professional.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.