7 Reasons Why Air Conditioner Smells Musty

So, you’ve been running your AC for a while now, could be that you’re experiencing a heatwave, you like the way it feels, or maybe you want a chance to cool off after a particularly hard workout.

But then, it hits you. Like someone dropped something rank in your room, and you search to find the source. Following your nose, however disgusting or annoying it is, you find the reason why the air is now filled with musty snuck.

It is your AC unit, and it might need repair.

See, the reason or reasons as the case may be why your AC smells musty when you turn it on because of either a single or multiple causes. 

So, for the moment, let’s go over some of the most common problems and a few that require your attention more than others. Keep in mind, if the AC smells terrible to the point you notice it all the time, then it’s a good rule of thumb to investigate. 

If not, then you most likely have a problem on your hands that may result in damage to your home, person, or loved ones.

If you find any significant damage to your AC unit, please consult an official technician or repairman to fix it.

Please note that while some are fixable by yourself, it is best to leave this sort of thing to professionals. 

1. Frozen Evaporator Coils

Evepatoator coils are what allow the Air Conditioner unit to process cool and warm air. See, AC units work by drinking the ambient air of the room and cooling it, removing the humidity, and then recycling the air back into the room. 

They can do this by the grace of their air filters, which is the entire reason why they can work in the first place. Without them, the AC unit will stop working entirely. 

See, when the Eveaptorior coil, or filters depending on which you prefer, get clogged from the dirt they’re taking in via their recycled air, that causes them to build up and block any new air from entering. 

The moisture build-up causes water to drip down the machine’s interior, which any technician can tell you is a bad idea and lands in the AC unit’s refrigeration. 

The latter bit allows the AC unit to cool the air and works as a central part of the entire machine. Should the filters become too clogged up to function, it’s best to clean or replace them as soon as possible.

2. AC unit is the Wrong Size

See, depending on the size of your home, the AC unit you have may not work as intended. There could be nothing wrong with the machine, but your home may be too big or too small for the unit. For example, if the home is too small, the Ac unit won’t recycle as well as it should. 

A big one cycles too quickly, resulting in a build of moisture that will affect the refrigeration, as stated before.

If that happens, try to call a technician and get the correct square foot for your home. You also need to know the number of people that live inside the home, on average. You also need to factor in the climate (not just the weather daily, but the climate of the area you live in), how tall your ceiling is because the air will go up.

You also must know how the insulation works, like, what kind of material is used for the walls. A room that allows for more airflow might have lesser build-up, and material that can absorb water may interfere with the air cycle.

3. Full Drain Pan

So, much like dust collect in a laundry machine, an AC unit will gather moisture and water regardless of your best attempts to clean it. The Drain pan is the component that will allow the moisture to be collected without harming the rest of the machine.

But, like any machine, it will suffer from continued usage that will decrease its effectiveness. When accumulated water is sitting for a long period of time, mold will occur. Which, in turn, is responsible for the musty smell you can sense. 

4. Electronic Components Shorting Out

As said before, moisture builds up, but that same moisture can affect the AC’s machine parts, potentially causing a fire hazard. Like any machine, certain parts cannot be touched by water at all or failing, they are designed to be at least water-resistant. 

If these parts catch fire or are otherwise touched by moisture, you’ll smell gunpowder or burning plastic. You’ll need to turn the AC off immediately and contact a professional technician to see the extent of the damage.

5. Dead Critters

So, we all know the old saying, “finding skeletons in the closet?” Well, you might find dead animals or insects in your AC unit. It’s not too surprising unto itself, as we all find spiders and ants crawling pretty much anywhere. 

In massive AC units, you might even be unlucky enough to find a rat, and I don’t envy you if that happens. Like always, you can tell by the smell, and if you happen to find a dead rat, best to call pest control to find out how this happened and what you can do to prevent it.

6. AC Leaking Gas

One of the most vital things that many households have is the gas, which powers the Ac, kitchen (if you have it), and fireplaces. So, if you start to smell something rank in your home, specifically something like a skunk, then your AC might be leaking gas.

That is, naturally, remarkably badThe very first thing you need to do if this happens is to cut off your gas to the house and find a utility to repair the machine.

7. The Condensate Line Might be Blocked

The condensate line allows water to be displaced from the drain pan and into the landscape or storm drain if connected. But it’s also one of the areas most likely to be clogged up with mold or sludge.

To prevent this, make sure the line is cleaned at least once a month. Before you do, make sure to turn the AC off, remove the thermostat and breaker panels, and then detach the condenser line and pour white vinegar down the opening. Let it sit for thirty minutes, and then reattach it. 

So, let’s have a Recap

If the AC unit is starting to smell musty, that means that a part of the machine has become broken, clogged up, or has grown mold. In this case, it is best to turn the machine off and attend to the blocked parts. You can usually clean these by yourself and be attended to once a month, but please be careful when doing so.

Others require a more professional approach, such as a gas leak or dead animals. If that happens, you should cut off all power to the AC unit or gas if the need arises, and call a professional as soon as possible.