How to Fix a Musty Air Conditioner

Brad Smith
Written By Brad Smith

Ever been hit by an unpleasant, musty smell as you walked into a room of your home and traced it back to your air conditioner? You’re not alone! For most homeowners, this common problem is more than a mere inconvenience; it’s an essential alert to the health of your air conditioning system.

Musty odours often indicate that mould and mildew are growing in your AC. Aside from being a bit off-putting, this can be particularly risky to the health of people with allergies or respiratory conditions. Fear not, though! Let’s explore some straightforward solutions to nip this issue in the bud, and get your home smelling fresh and healthy once again.

how to fix a musty air conditioner

Understanding the Cause

As we’ve established, the presence of mould and mildew in your air conditioner typically accounts for any funky smells that come from it. Both thrive in damp, dark places, and your AC unit, with its nooks, crannies, and moisture, is stacked with them. 

But why the moisture? Well, as your air conditioner cools the air, it also pulls moisture from it. If that moisture doesn’t drain away, it builds up in the system. Throw in some dust and debris that sneak in over time, and you’ve got the perfect recipe for that musty odour. 

Safety First

Before you roll up your sleeves to tackle that stinky air conditioner, let’s talk safety. It should go without saying, but I’ll say it anyway – safety is paramount.

First and foremost, switch off the power supply to your unit. This isn’t just about preventing electric shock. It’s about ensuring you can work without the system suddenly working without warning. While we’re talking protection, don’t underestimate the power of a good pair of gloves and a mask. These simple accessories can shield you from dust, mould, and any other airborne irritants you might encounter. Remember, tackling the issue safely is just as important as fixing it!

Cleaning or Replacing the Air Filter

One of the first all-important steps toward conquering that musty odour is the air filter. This essential part traps dust, pollen, and other airborne particles, and prevents them from clogging up your system. However, dirty filters can become a breeding ground for odour-causing mould and bacteria. Cleaning or changing air conditioner filters goes a long way towards avoiding this. 

It’s worth checking your filter monthly and cleaning it if it’s washable. Just a gentle rinse under the tap will do, followed by a thorough air-dry. If it’s disposable, make sure to replace it with a new one. Maintaining clean air-con filters both prevents musty odours and helps your system run more efficiently. Win-win! 

Checking and Cleaning the Drain Pan and Line

Next up, let’s turn our attention to the often-ignored drain pan and line. 

The drain pan gathers condensation from the air conditioning unit, while the line makes sure that moisture leaves your home. However, if either part gets blocked or overflows, you’re in for a smelly mess. Check these components regularly for any signs of standing water or blockages. A simple clean can often fix this; gently flush the line with a mixture of water and bleach to kill any lurking mould or mildew. 

Keeping these areas clean not only keeps odours at bay but also protects your home from potential water damage.

Inspecting and Cleaning the Coils

Your air conditioner coils play a pivotal role, with the evaporator coil drawing heat from the air and the condenser coil releasing it outside. However, these coils often gather dust and grime. This results in a drop in their efficiency, and they can start harbouring mould, leading to that musty scent we’re looking to conquer. 

Addressing this is relatively easy. Gently brush off any loose debris from the coils and then apply a coil cleaner. Be sure to follow the product instructions carefully. This will help to eliminate odours while also ensuring your AC runs smoothly and efficiently

Ensuring Proper Ventilation

In the fight against the scourge of the musty air conditioner, proper ventilation is the true MVP. Ensuring you have suitable ventilation keeps the air moving and prevents moisture from becoming your unwanted house guest. 

Make sure your AC unit isn’t boxed in. Just as we need room to breathe, so too does your air con. This means keeping furniture, curtains, and other potential obstructions well away from the unit and its vents in the ceiling. On a broader scale, consider the ventilation in your entire home. Periodically opening windows to let in fresh air can do wonders. It reduces humidity levels and ensures a constant flow of fresh air. This not only helps in keeping musty odours at bay but also contributes to a healthier living environment.

When to Call a Professional

There comes a point when the DIY approach meets its match, and it’s time to call in the big guns. If you’ve given your AC a thorough clean and the musty smell lingers, or if you’ve encountered anything that looks more complicated than anticipated, don’t hesitate to get expert help. 

Professional air conditioning technicians have the tools, knowledge, and experience to diagnose and fix deeper issues that might be beyond reach. It could be anything from internal component faults to ductwork problems. Regular professional maintenance can also prevent future odours and extend the life of your air conditioner. 

Breathe Easy: Your Guide to a Fresher Home

And there we have it! By following these steps, you’re well on your way to waving goodbye to that pesky musty smell from your air conditioner. Remember, the key lies in regular maintenance and being proactive in addressing any signs of moisture or mould. 

A clean, well-functioning AC unit not only ensures your home smells fresh but also improves air quality, making your living space a healthier and more comfortable haven. So, take action, stay vigilant, and enjoy the clean, cool air that your air conditioner was meant to provide.

smith brad omni

Written by Brad Smith

CEO & Lead Interior Designer

Brad Smith is an experienced interior designer and the founder of With a Master's degree in Interior Design from Pratt Institute and a passion for creating safe and healthy living spaces, Brad shares his expert insights and innovative design ideas with our readers. His work is driven by the belief that home is where every story begins.