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Why does my car’s A/C smell bad?

Air conditioner odor complaints are a common consumer problem. Why?
A/C system odors typically result from uncontrolled growth of bacteria and other microorganisms in the evaporator part. Nasty little beasts like aspergillus, cladesporium and penicillium grow on cooling coils and other areas. How do these beasts get there?
They are naturally present in outdoor air and are drawn into the system through the evaporator during system operation.
Moisture also contributes to A/C odor formation. Most of it that condenses on cold surfaces inside the system drains harmlessly over time. However, some moisture continues to cling to coil surfaces after the A/C shuts down.
Microbial contaminants in the air combine with this lingering moisture in the evaporator. The warm, dark and moist conditions in the evaporator provide an ideal breeding ground for bacteria, mold, mildew and nasty beasts to grow and generate musty odors…think about old sneakers left in a locker over the summer! Stinky!
Tomorrow …how to cure the odor.
When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.
You can E-mail us at or visit to find a Mobile Air Conditioning Society repair shop in your area. Visit to find out more about your car’s mobile A/C and engine cooling system.
Thanks to MACS member Airsept inc. for this blog contribution on understanding A/C system odor.

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