5 Reasons Your Air Conditioner Smells Bad

Are you bothered by an unpleasant smell in your home that seems to only worsen when you turn the air conditioner on? While your priority might be to address that horrible odor and eliminate it, you should know that the problem goes beyond that smell and could actually be serious enough to cause health issues.

But why does your air conditioning unit smell bad in the first place? Here are some of the potential culprits:

Mildew, Mold, and Must

If there is an excessive amount of moisture and humidity in the HVAC system, it’s highly possible for mold and mildew to grow and start flowing through the ductwork, too. To avoid such problems, make sure that you address water leaks, stay on top of your HVAC maintenance and tune-ups. Don’t forget to replace your HVAC filters, too.

If there’s exposed earth in the basement or crawlspace, find ways to have that covered.

You should also have a whole-home dehumidifier that is directly connected to the HVAC system.  This will automatically get rid of the excessive amount of moisture from the air and then deposit the condensate outside of the home.

Cigarette Smoke

If someone in the house smokes, the bad odor could accumulate both in the evaporator coil and the filter. That’s why you smell cigarette smoke the moment you turn on the air conditioner.

The answer to this problem is to replace the filter, have a professional tune-up and cleaning done, and avoid smoking indoors in the future.

Something Burning

If you smell smoke or burning, then there’s probably a reason for that – whether it’s an overheating motor, a short from either the fan motor or the circuit board, a wiring problem, or something else. Whatever the cause is, the smell of something burning is a sign of a serious problem that you should not ignore.

Take your family out of the house and contact the fire department and the HVAC expert. Also, don’t forget to turn off the HVAC system as soon as you smell something burning that you suspect is coming from it.

Critter’s Carcass

If you smell something really rotten, it’s possible that a critter has died in either the duct system or the HVAC system. You won’t be able to ignore the horrible smell so you need to find the carcass and get rid of it. Of course, you’d have to turn off your HVAC system. Then, open some windows and doors to ventilate the area.

It’s also a good idea to call a professional pest control company apart from the HVAC contractor to address the problem.

Gas Leak

The smell of rotten eggs in the house should never be ignored because it could be coming from leaking gas. Natural gas may be odorless, but manufacturers are required to add mercaptan to give the gas that distinct rotten-egg smell.

If this is what you smell, evacuate your family at once. Turn off everything electrical in the house. Don’t use a match or a lighter and put out any open flame. Open all the doors and windows and turn off the gas supply right at the meter. If you don’t know how to do it, immediately call the gas company. Do not attempt to turn the gas on again and allow the gas company to do it for you.


Poor quality of indoor air is among the biggest threats to the health of Americans. From the dust, dirt, fungus, microbes, molds, and mildew that could form in the HVAC system, and other causes of damage, the effects go beyond the unpleasant smell coming from the air conditioning unit.

If you notice any of these smells coming from your air conditioner or any other problem with the HVAC system, make sure to call reliable professionals from Good Guys Home Service who can provide you with expert air conditioner services. Contact us today and we’ll connect you with professionals who can help you!


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