Why Your AC Unit Smells Musty and How To Fix It

If your AC unit smells musty, you’re facing something bigger than an unpleasant odor. This recurring concern could mean potential health risks and HVAC performance issues, so you don’t want to leave it to continue.

How can you stop smells from overtaking your HVAC system? As your trusted provider of AC repair in Louisville, KY, A1 Mechanical Heating & Cooling encourages you to investigate the causes of these strong odors. Read more below about creating a cleaner, fresher indoor environment. 

Warning Signs That May Accompany a Musty Smell in Your Cooling Unit

When an AC unit smells musty, you’ll need to determine whether the smell needs immediate attention or will go away on its own. Louisville, Kentucky, doesn’t require indoor cooling in the winter. Do you leave your air conditioner off during this time?

If so, those long months of disuse can cause excess moisture within the system. When you turn your air conditioner back on after the winter, you might detect a musty smell during the first few cycles, but it should dissipate after that. A persistent odor isn’t a good sign and might accompany other worrying symptoms, such as:

• Poor or lukewarm airflow from your vents
• An excessively humid indoor environment
• More dust settling around your building than usual
• Cooling cycles that last too long or not long enough

If an AC unit smells musty and shows these signs, the issue won’t go away by itself.

Why Your AC Unit Smells Musty

A sour or musty AC smell typically indicates that mold and mildew growth has overtaken your cooling system. Mold spores are a concern in and of themselves because they can lead to countless health concerns, including:

• Constant nasal and throat congestion
• Persistent urges to sneeze or cough
• Pressure headaches
• Recurring allergic reactions
• Worsening respiratory or autoimmune conditions

It could mean anything from a filthy filter to a clogged drain line, but the presence of mold or mildew can also be a symptom of a bigger HVAC problem. Let’s examine some troubleshooting methods below.

What Can You Do About It?

You can keep nasty odors and other comfort and efficiency issues at bay by giving your cooling system some regular attention. Our Louisville technicians recommended a few simple measures you can take to protect your air conditioner throughout the summer. Don’t forget to do the same for your furnace to achieve the best performance and the freshest indoor air.

Replace the Filter Quarterly

Dirty air filters are easy to forget, but they will remind you of their presence by their smell. Filters capture particles from the air as the return register pulls them back into circulation. This makes your air cleaner and healthier, but most basic disposable filters only last a few months at best. 

A good rule of thumb is to replace the filter every three months or according to your HVAC provider’s recommendations. A filter caked in dust and other debris enables mold to settle and reproduce. 

Inspections When You Switch the Filters

When replacing your air filter, go ahead and inspect every visible part of your cooling system. If your AC unit smells musty, it might have mold growth and moisture buildup in other areas. Specifically, check the following components:

• The condensation drain system: The bottom of the pan might have some mild moisture, but it shouldn’t be filled to the brim. A full pan means a clogged drain, which increases moisture. 
• The base of the outdoor unit: Look for signs of water trickling away from or pooling around the unit’s base. This could mean frozen or dirty coils and refrigerant problems.  
• The surfaces surrounding all duct openings: Check for water stains or dampness around each vent grate and the wall or floor surrounding it. Condensation from a fractured duct could pool and trickle from these openings.

If you discover any of the above concerns, turn off your air conditioner and contact an HVAC technician to resolve the issue. 

Open and Unblock All Vents

During your quarterly inspections, you should also make sure each vent is fully opened with no obstacles blocking airflow. Why? A closed vent in one room prevents the system from distributing cool air evenly, which means more heat and humidity in that particular room. 

Balanced airflow is essential for a well-ventilated building with no moisture buildup. An area that doesn’t have even cooling is also more vulnerable to mold growth, which will make that musty odor return. 

Clean the Visible Equipment

Both indoor and outdoor equipment can gather lots of debris. Think about how often you mow the lawn or the amount of leaves that fall in autumn. This organic matter can gradually encase the outdoor unit, keeping air from freely exiting.

Meanwhile, your indoor unit can overheat from excess dust covering its surface or storage items crowding it. Debris and belongings insulate it, trapping moisture and potentially coating coils or creating clogs in the drain line. 

If your AC unit smells musty or, worse, like decay, it might have decaying organic matter jamming it up. Remove leaves, twigs, and grass clippings from the outdoor equipment and use a soft rag to gently wipe down the indoor air handler. Provide each unit with at least two feet of clearance on all sides. 

Schedule HVAC Maintenance Every Six Months

While the above tasks can assuage many sources of foul smells, only HVAC system maintenance can address internal components. Your system needs twice-annual visits in the spring and autumn to address the following maintenance needs:

• Condenser and evaporator coil cleaning
• Duct inspections
• Hardware adjustments
• Lubrication for moving parts
• Fan blade dustings

The technician will also handle a filter change during their visit and recommend additional measures to improve your air quality and fight odors. For example, some buildings benefit from dehumidifiers and additional ventilation for fresher air. 

Start With A1 Mechanical Heating & Cooling’s Air Conditioner Maintenance Services in Louisville, Kentucky

When your AC unit smells musty, your AC is not blowing cold air, or things are cycling strangely, call A1 Mechanical Heating & Cooling at 502-708-2247! We provide HVAC maintenance in Louisville, Kentucky, and the surrounding areas.