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How to Remove the Musty Smell From Your Air Conditioner

Musty smells coming from your air conditioner is a major sign of mold and mildew growth. This can be dangerous to your home and healthy, so you’ll want to figure out how to remove the musty smell from your AC as soon as possible.

We’ve put together this article to help you do it. Your musty smell could be coming from bacterial growth on your drain, evaporator coil, drain pan, or drain line. We’ll provide you with detailed instructions covering how to figure this out in the sections below.

Here’s how to remove the musty smell from your AC

Step 1: Begin by turning the unit off

The first thing you’re going to want to do is turn your air conditioner off. This is for safety purposes, so be sure not to skip this step. You may even want to unplug the power cord if possible, just to be on the safe side.

Step 2: Clean the inside of your AC thoroughly

Once your AC is off, you can get started on cleaning the inside of the unit. You can begin by removing the door that’s found on the side of the unit, which you may need a screwdriver to do.

After that, you can clean the evaporator coils by rubbing them with a cloth or soft brush so that you remove any dust that you see.

Once that’s done, take the next step by removing the drip tray, which you should be able to find underneath the unit’s coils. You may see some water and even some mold in it.

If your drip pan has mold in it, that’s a sign that it’s no longer effective. You’ll want to call out an HVAC technician to replace it with a new one to ensure that the problem doesn’t happen again. That being said, it’s easiest to clean your drip tray with a little water and bleach.

Finally, you can finish up this process by making sure that the evaporator line is totally cleared out. You can do that by using a wet vacuum to suck out anything that may be inside of it. You should be able to find your evaporator coils near the air handler.

Step 3: Clean out your condensate drain line

The next thing you can work on is clearing out your air conditioner’s condensate drain line. You can begin this process by poking a finger up the drain line and seeing if you notice any clogs that you can dislodge that way. Your condensate drain line should be located next to the air handling unit, which is often in the garage or attic.

As part of this process, you’ll also want to remove and clean out the vent tee. This is an important access point, which may contain some build-up.

You can use a wet/dry vac to clear out any blockage here. Depending on the type of vent tee that you have, you may need to wrap something like a wrap around the end of it to form a seal so that the vacuum works properly.

Once you’re done vacuuming out any materials, you can use water to completely flush out the condensate line so that it’s totally empty. You can even use some vinegar to break down any build-up that may remain. Just a few cups of it down the drain line should do the trick, as long as you let it sit for about 20-30 minutes.

Finally, to avoid experiencing a similar problem in the future, you can use drain pan tablets so that the growth you’ve just cleaned out won’t come back.

Step 4: Find the filter

If you want to remove the musty smell from your air conditioner, the filter is another place you’ll want to look. It’s typically located near the thermostat or close to the air handler. It could be in your walls, underneath a window, on the floor, or even in the ceiling. It just depends on your home’s construction.

If you need help finding the return vent where your air filter could be, hold up your hand to the vents in your home while the AC fan is on. If you feel a suction effect, that’s a return vent.

An air handler is a big metal box that houses both your system’s fan and its motor. It’s usually located in the attic or basement, and the filter will be somewhere within it.

One thing to note about your air handler is that it may have directions about how to insert the filter. So be sure to look while you’re inside of it.

Step 5: Replace the air filter

Once you’ve found the filter, you can get to work on replacing it. Here’s how to do that:

  1. Make sure you know the size of your filter first. It may tell you this on the old filter, or you can use a measuring tape to figure it out yourself. You can also look it up online if you know the manufacturer’s name.
  2. Next, remove the old filter by gently pulling it out.
  3. Install the new filter in the same way that the old one was situated in your system.
  4. Be sure to note the arrows on the filter, as this will show which direction the air flows. You want the air to flow into your system, not away from it.

Step 6: Turn off your outdoor AC unit

Now that we’ve tackled some of the potential sources of mustiness coming from your indoor unit, it’s time to move our work outdoors.

The first step is turning off power to the outdoor unit, which you can usually do by flipping the breaker switch outdoors. It should be located under a flip-up lid somewhere close to your condenser.

Step 7: Take off the top of the condenser unit

The next step is taking off the top of your condenser unit. You can figure out how to do this by looking at your system’s manual.

Step 8: Remove any debris that you find

You may see some debris when you first open up the condenser unit. You can start by removing that. It may be helpful to use a vacuum that can suck up things like grass, dirt, and leaves.

You can also blow compressed air to clean this out in tough-to-reach spots. Just make sure to do it from a distance so that you’re not damaging any internal parts in the process.

You can finish up with a small brush or cloth to get anything that’s left.

Step 9: Clean out the AC coils and fans

Next up, you can focus on cleaning out the AC coils and fans. To do this, you’re going to need a coil-cleaning solution, which you can typically find at a home improvement store or online.

One thing to note about this is you can’t use the coil-cleaning solution on indoor coils. That’s because the fumes are toxic, so it would be dangerous to do so.

Follow the directions on the cleaning solution to dilute it. Then, add it to your pump sprayer and begin applying it to the coils. You should see it foaming up within a few minutes, and you can wash it off with a hose once that’s complete.

Make sure that you don’t use a pressure washer for this, because it could damage your fins, which are delicate.

Step 10: Spray the unit down

The next thing you can do is spray down the unit entirely. This should help to get rid of any remaining dirt and dust.

When you do this, be careful not to get the electrical box wet. And finish up by flushing out the drip tray to get rid of any dust or debris that may have accumulated in it.

Make sure not to use a pressure washer for this task either, as it could also cause damage.

Step 11: Give it time to dry

This step is pretty straightforward. You’re going to want to give your unit some time to dry off before putting everything back together.

Step 12: Put the unit back together

Once your system is dry, you can put everything back together so that it’s the way it was when you first began working on it.

What else you can do

If you do end up having moisture and dirt in your unit, then those can easily spread throughout your home since that’s what your HVAC system is designed to do. There are a few steps you can take to get rid of any lingering musty smells that may still be present in the home.

Here’s what to do:

  • Open up windows so that you start getting fresh air into your home.
  • Get rid of any water leaks or sources of standing water in your home.
  • Use a dehumidifier to get rid of any excess moisture that may be in the air.
  • Use a vacuum and mop to get rid of any lingering odors from your floors.
  • Use vinegar in a spray bottle to wipe down surfaces.
  • Don’t use steam cleaning, as it could cause damage.
  • Make sure that your drain pipe slopes downwards towards the drain.
  • Remove any fiberglass or insulation material that appears wet or moldy.

Do you need your air ducts cleaned?

When you have a ton of excess moisture in your unit, that can sometimes cause mold and mildew to settle in your air ducts.

If you smell mustiness as soon as you turn on your AC, that’s a big sign that you may have mold and mildew in your ductwork. You would want to get these cleaned if so.

That being said, you may not need to clean your air ducts. If there’s no one in your house suffering from unexplained allergies and you can’t see any deposits of mold, then this may not be necessary.

Dust is somewhat normal. But alone, it’s not a sign that you’ve got any mildew or mold. You can fix it with a simple vacuum.

The bottom line is that you may need to have your air ducts cleaned by a professional if you notice these symptoms:

  • You can visibly spot mold in your air ducts.
  • You’ve got a problem with pests in your air ducts.
  • You’ve discovered that your air ducts are full of dust to the extent that it’s impacting your ability to use your HVAC system.

Make sure that your unit is the right size for your home

As you think more about how to remove the musty smell from an air conditioner, you’ll also want to verify that you have the right-sized AC unit for your home.

When your air conditioner is too big for your house, it will cycle the air too quickly. This creates a situation in which the AC unit turns on and off rapidly. And when that happens, your system’s dehumidifier won’t work properly, so you’ll typically get excess moisture in your home.

The cooling power of an AC unit is typically measured in British Thermal Units (BTU) per hour. One ton of heating or cooling capacity is equal to 12,000 BTUs/hour.

This is a measurement that you need to take into account while purchasing a system for your house. Your needs will vary based on the size of your home, its ceiling height, and the number of people that live in it.

If you’re not sure what BTU rating you need, then you may want to check with a professional. They can consider all of the unique factors associated with your home to give you a definitive answer.

Avoiding this problem in the future

Once you’ve successfully gotten rid of the musty smell in your home, you’re going to want to be proactive to make sure that it doesn’t happen again in the future.

The best way to do this is to be consistent about maintaining your HVAC system. You can also schedule regular checks for common problems, such as icy coils and weak airflow.

Michael Joseph