Most people turn on their air conditioners to get some relief from uncomfortable temperatures. That relief doesn’t last long when you quickly notice a musty smell coming from your vents. So, what does it mean when your air conditioner smells musty when first turned on?

Check the air filter if you notice your air conditioner smells musty when you first turn it on. Dirty, dust, pet hair, and even mold or mildew can build up on your air filter. A flooded drain pan can also explain the musty smell that comes from your air conditioner. A musty smell can also appear if the evaporator coils are moldy or frozen.

Unfortunately, the smell may also be due to a dead pest in your air ducts, such as a rodent. In that case, an HVAC technician must get rid of the pest and clean your ductwork. Follow along as we explore why your air conditioner smells musty when first turned on.

Why Does My AC Smell When I Turn It On?

Whether it be a dirty air filter or frozen evaporator coils, your air conditioner may smell musty when it’s first turned on for many reasons. Most of the causes are fixable, but it’s best done with the help of an HVAC technician. Let’s explore the reasons why your air conditioner smells musty when it runs and see how to fix it.  

Dirty Air Filter

Air filters protect you from dirt, dust, debris, and pollen that would otherwise circulate throughout your home. Over time, the combination of moisture and debris can create the perfect conditions for mold and mildew. You can tell that is the case if your house smells musty when you first turn on the air conditioner.

This is an easy problem to avoid if you change the air filter every 90 days. Some homes are more susceptible to mildew and moldy air filters, especially if your home is quite humid. In that case, you may need to change the air filter more often.

Moldy Drain Pan

An HVAC system’s drain pan collects condensation as your AC runs. This condensation collects in the drain pan to protect your home and AC unit. The drain pan can fill up quickly, especially in humid areas or if the drainpipe is clogged.

Drain pans can become moldy when the water sits for too long. Check your drain pain if you smell a moldy, mildew smell when you turn your AC on. This is more common during hot and humid summer days. Many homeowners never need to empty their drain pans.

However, you must check the drain pan if you smell mold when your air conditioner runs. Empty the pan and inspect the drainpipe for clogs. Never attempt to clear a clog in your drainpipe without an HVAC professional’s help. You may accidentally damage the pipe which can lead to expensive repairs.

Pests in Your Ductwork

Did you notice a musty that is slowly becoming worse? If so, this good be a sign that there is a dead pest in your ductwork. Rodents can climb into your home’s air ducts, struggle to get out, and eventually die.

The smell originally starts musty, but it eventually becomes rotten and hard to stomach. An HVAC technician can easily inspect your ductwork and remove the dead pest. From there, they must clean the duct to remove any traces.

However, you may still notice a musty smell at first when you run your AC next time. Luckily, the smell will pass shortly, and you shouldn’t smell it again.

You Haven’t Run Your AC in a While

Did you run your AC for the first time of the season, and it smells weird? If so, you won’t likely have anything to worry about as this is normal. Much like a furnace, dust can settle in on several components of your AC when you don’t use it, such as the coils.

A musty smell is normal when you run your air conditioner or furnace for the first time in the year. The musty smell should go away within a few minutes. If it continues, you may simply need to replace the filter or have an HVAC technician clean the evaporator coils.

Frozen Evaporator Coils

Frozen evaporator coils may fill your drip pan, but that’s not the only way they can create a musty smell. While some of the condensation goes to the drip pan, it can also drip around the base of the unit. This will create moldy conditions within your home.

The mold and mildew smell can make its way into your AC and spread through your house when it runs. Drain pains can flood because of frozen evaporator coils, and this can cause water damage around the system. Your AC will also run more often and produce warm air instead of cold air if the evaporator coils are frozen.

Luckily, it’s typically easy to thaw the ice on evaporator coils. However, you must be careful as water will accumulate. You must also treat the root of the problem, such as dirty coils or poor airflow, or else they will freeze again.

Dirty Air Ducts

The air ducts in your home carry air through your home when you run the air conditioner or furnace. Air isn’t the only thing that moves through the ductwork, however. Dirt, dust, debris, and pet hair also move through your home’s duct system.

The combination of debris, darkness, and moisture creates mold conditions. You can smell the mold and mildew when you first turn on your air conditioner. Have an HVAC professional clean your ducts every 3-5 years, or sooner if you smell mold coming from them.

So, Why Does My AC Stink When I First Turn It On?

The main reason your AC smells musty when you first turn it on is that the air filter is dirty. It’s normal for an AC to smell musty when you run it for the first time of the season because of the dust buildup. Otherwise, the musty smell could be because of a flooded drain pain, dirty air ducts, and frozen evaporator coils.

When it comes to entrusting your HVAC needs to professionals, experience matters. At Rich's Heating And Cooling LLC, we bring decades of collective expertise to the table. Our seasoned team comprises industry veterans who have meticulously honed their craft over years of hands-on experience. From routine maintenance to complex repairs, we've navigated the diverse challenges of the HVAC realm with unwavering precision and dedication. With every project, our commitment to excellence shines through, ensuring that your comfort and satisfaction remain our utmost priority

Ready to eliminate that musty smell and ensure your AC runs smoothly? Don't wait any longer. Contact Rich's Heating and Cooling LLC today at (732) 433-0068 for expert HVAC services tailored to your needs. Let our dedicated team provide you with the comfort and peace of mind you deserve.