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What Is That Odor Coming From Your AC?


A suspicious or unpleasant smell in your home can be hard to ignore, especially when you walk in the door from outside and the odor assaults you. If that smell is coming from your air conditioner, you need the help of a qualified technician to get it sorted out. But what could cause an air conditioner to make a bad smell? What in the world is wrong? We’ll explain the most likely culprits.

A Sweet, Chemical Smell

If the odor you’re detecting has both a chemical sharpness and a hint of sweetness, it’s refrigerant. This is the substance which absorbs and releases heat as it flows through the coils, in and out of your home. If a coil is damaged or has deteriorated, it can allow the refrigerant to seep out, making a noticeable smell.

Don’t ignore it! Insufficient refrigerant means insufficient cooling. And if your system can’t get your house cool enough, it will keep running more and more, putting excessive strain on the compressor. You need to get that coil repaired and refilled promptly.

A Hot, Plasticky, or Fishy Smell

Hot dust odor is a sign of overheating, probably in the blower fan motor. If it starts to smell like overheated or melting plastic, it may have gotten bad enough that the wires in the motor are literally melting and beginning to fuse together. And if you smell fish, though this may seem strange, it is a sign of an electrical fire, which can release ammonia into the air.

Any of these odors mean there’s a problem that is causing a fire hazard. Turn off the air conditioner! A qualified technician can determine exactly which component is overheating. Whether you need a thorough cleaning, a new blower fan motor, or some rewiring, this is definitely a job for a professional.

A Sour or Mildew Smell

As the refrigerant flows through the coils, it has to be very cold in order to absorb heat from your home. This means that the surface of the coils will pull condensation out of the air, just like the surface of an icy-cold drink can. Your air conditioner has a condensate pan to catch that moisture, and a drain to safely remove it from your home. 

The unpleasant reality about anything that spends a lot of time being moist is that it’s an ideal environment for some not-so-lovely things. If mold grows there, you’ll notice a mildew smell. If what’s growing is a colony of bacteria, it can smell sour, like vinegar. 

Either way, it needs to be dealt with before it clogs the drain and overflows the pan or triggers the system’s automatic shutdown. This will probably only require cleaning, but it must be done by a technician. They will have to disassemble the unit to properly eliminate the problem. 

Avoiding Odors in the Future

Routine maintenance, generally done in the spring, is the best way to prevent any of these problems. During maintenance, your technician will clean away the dust that could cause overheating and the mess in the condensate pan. They’ll inspect the coils for potential leaks and test all the electrical components. 

Whether you’d like to schedule annual maintenance or you need air conditioning repair in Cambridge, MA, we’re ready to help.

Reach out to Cooling Unlimited, Inc. to speak with qualified AC experts.

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