Why Does My Air Conditioner Smell?

Why Does My Air Conditioner Smell?


With February coming to an end we are inching closer and closer to air conditioning season. Hooray for short Southern winters! But sometimes, things can be a little “off” with your air conditioner. It might start by noticing a subtle odor, and then one day you come home from work, and something smells.

Is that smell musty? Does it smell like dirty socks? Or maybe it has a hint of rotten eggs to it. Believe it or not, these differences matter – the type of smell is a big indication of what is going on with your air conditioner. Narrowing down the issue is key to solving the problem, so let’s look at the things that can create an unpleasant smell in your HVAC system.


Your Condensate Drain is Clogged

One of the reasons we advise our clients to do bi-annual inspections on their HVAC systems is to ensure that their systems are clean and free of clogs. But sometimes homeowners forget to schedule inspections and the next thing you know there is a blockage in the condensate drain.

This drain is located on the outside portion of your A/C unit and can become blocked for several reasons. Storms can cause minor flooding, forcing debris into places it just doesn’t belong. Algae, mold, and mildew can also build up, causing a clog and creating an environment for even more fungal growth. Gross.

A clogged condensate drain usually creates a musty smell. If this is the problem, it’s a very easy fix. There are DIY videos for cleaning the drain online, but if you aren’t a DIYer, a pro can clean it out as part of a routine inspection.


Your Coils Are Dirty

So, it looks like the condensate drain is clear, but you are still smelling something that can only be described as dirty socks. It’s possible that the problem is related to dirty evaporator coils. These coils are located within the portion of your air conditioner that is indoors. Sometimes enough moisture builds up on these coils to allow for mold growth, which can also trap and hold bacteria. Over time, this can create a smelly situation.

Like the clogged condensate drain, this is a relatively easy fix that can be done by an ambitious weekend warrior. Or, if you’d prefer, a professional can come out and do a thorough clean of your whole system to double check for another potential mold build-up source.


Your Air Conditioner is the Wrong Size

If you’re smelling dirty socks, there may be a chance that your air conditioner is the wrong size for your home. Air conditioners play two roles – they cool your home, but also act as a dehumidifier. If your air conditioner is too large for the space it is meant to cool; the cooling cycle may complete too quickly, leaving too much humidity in your home and ductwork.

And what loves a moist environment? Mold and mildew.

If mold and mildew begin to build up in your ductwork, it can definitely create a dirty sock odor that just won’t quit, not to mention the health problems posed by fungi spores blowing throughout your home. No one wants to breathe that stuff! A professional can help to clean or replace your ducts, depending on the severity of the buildup. From there, a pro will work with you on determining the best way to solve the size issue with the cooling unit.


You Have a Dirty Filter

Have we told you to change your air conditioner filter recently? We discuss filters again and again on the blog because dirty filters can be such a source of maintenance issues for HVAC systems, including issues with smells.

If you haven’t changed your filter in quite some time, take a look at it. Can you even see the filter through all the dust and debris? All that debris can cause airflow issues and creates a fantastic environment for mold, mildew, and bacteria to live. As air blows through the filter, all that stuff is going into the environment of your home and perfuming your living space with a lovely musty smell.

A dirty filter is an easy problem to solve – check your filters monthly and change them if they are dirty. A fresh filter will help to keep your home smelling clean, not to mention improve the overall air quality of your home.


You Have an Unwanted Visitor

If you come home to the smell of rotten eggs, it’s time to call in pest control. This goes double if you have heard any weird scratching sounds coming from your ductwork, or if you have found animal hair or droppings when you remove your vent covers.

This smell is a sign of a pest problem. Either critters are currently living in your ducts, or an animal has potentially died in there. Pests are a problem that requires a professional. Don’t delay this call, as some pests can carry dangerous viruses that could cause major health concerns for you and your family.


Don’t Ignore Burning Smells

If what you are smelling can be described as “burning” or “gunpowder,” power off your air conditioner and call an HVAC tech immediately. These smells are usually an indication of a mechanical failure and electricity should be cut to prevent further damage to your system.

The only exception to this rule is when your heater is turned on for the first time during the colder months. In this case, a burning smell is caused by a buildup of dust during warmer months. This smell goes away quickly – if it lingers, there is likely a problem that should be handled by a pro.