Strange smells coming from your AC are more than just annoying—bad smells can signify serious problems with your AC unit.
If your AC is blowing out smelly air, the first thing to do is figure out what it smells like since the type of odor coming from your AC can help pinpoint the problem. The most common smells are:
If any of these odors are coming from your AC, keep reading to figure out the cause and what to do about it.
Burning smells coming from your AC can signify electrical problems. If you smell burning coming from your AC, turn it off immediately and call a professional to evaluate the problem and prevent further damage to it.
A burning smell is most commonly caused by overheating of AC components. Some standard components that experience wear and tear are the following:
- Fan belt
- Blower motor
Ignoring issues with these components can lead to electrical fires or severe damage that requires an AC replacement. Call an HVAC professional to lubricate, repair, or replace these individual components as needed.
Regularly changing your air filter can help prevent overheating in your AC unit. When your air filter gets dirty, it’s harder for your AC unit to pull in enough air to cool your home, making it run longer and contributing to potential overheating.
If you smell a chemical odor coming from your AC, it most likely means your unit is leaking refrigerant. Refrigerant is a toxic chemical, so an HVAC technician familiar with managing this dangerous substance should patch any leaks.
Other signs your AC might be leaking refrigerant are:
- Hissing or bubbling sounds
- Your AC is emitting warm air in cooling mode
- A sudden increase in your energy bills
After identifying and patching your leak, a professional will need to recharge (meaning to refill) your refrigerant levels to make sure the system has the correct amount. It’s important to get your refrigerant recharged—if your AC doesn’t have enough refrigerant, it won’t be able to cool your home effectively.
Musty-smelling air coming from your AC is often caused by mold or mildew growing in the unit. Mold can develop due to:
- Leaking ducts
- A dirty evaporator coil
- A blocked condensate line
If your ductwork has leaks and passes through areas of your home without air conditioning (like the attic), dust and dirt can enter it. When the dust and dirt touch warm and humid air, mold develops.
The evaporator coil is where heat transfer occurs, creating condensation on the evaporator coil. Typically, this condensation drips through a drain and is deposited outside. However, if the evaporator coil is dusty or dirty, the condensation won’t drain properly and can instead create mold.
The condensate line is the tubing that carries condensation from the evaporator coil to the outdoors. If the condensate line is clogged with dirt, condensation may back up in your AC and cause mold to develop. Other signs a condensate line clog is causing a musty smell are:
- Water puddling around your AC
- Your AC shutting off unexpectedly
Consult an HVAC technician to repair ductwork, clean the evaporator coil, and vacuum out any condensate line clogs. These AC components can be difficult to access and easy to break and should be left to a professional.
If your AC emits a rotting smell, there’s probably a dead animal trapped in your ductwork. Animals can enter your ducts through large cracks or leaks and become trapped.
An HVAC technician can carefully separate your ducts, retrieve the animal, and seal the leaks so animals and dirt can’t enter your AC system.
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