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Foreign Affirs Motorsport
Foreign Affairs Motorsport
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Why Does My Car’s AC Smell Bad When I turn It On?

Car's AC Smell Bad

Have you ever wondered why your car’s AC smells bad when you switch it on? In South Florida driving with the AC on has become a necessity as opposed to a luxury because temperatures outside are considerably warmer. There is nothing worse than getting into a burning hot car, only to be confronted by the foul smell the AC lets out when you turn it on.

If you are met with a stench that turns your stomach, there is certainly something suspicious going on, and it shouldn’t be ignored. By understanding the origins of these arduous odors, you can identify and get help treating the problem quickly and for good. You could be surprised by the causes of the bad smells creeping up your nostrils and how common they are.

Dirty Socks

When using the AC system full blast in your vehicle, it produces excessive water condensation which then collects inside the AC housing. The combination of water and the outside heat creates a favorable environment for mold, mildew, bacteria, and fungus to breed and grow. Air being forced out through the vents of your dashboard, floor, and window defroster, result in the “dirty sock” stench. As your vehicle gets older, or the air conditioner is used less frequently, micro-organisms or bacteria can begin to grow, and contribute to the nasty smell too.

It is best to take action and inject an anti-bacterial treatment into the AC conditioning case to destroy all living bacteria living in there. It is advised that you should turn the AC unit off and rather let the car’s fan run for a while instead so that the condensation build up can evaporate. The most effective way of preventing such smells is to invest in regular AC cabin filter maintenance.


If you are inhaling a sour smell, much like vinegar, the problem most likely could be caused by the electric motor emitting ozone. Other possibilities can be excessive water vapor, a malfunctioning filter, clogged condensation pan, or even mold.

Having a mechanic take a proper look at your car’s AC is the best bet. They will in all events start by replacing your AC filter, and treating the car’s AC system with an interior cleaner that uses enzymes to eliminate the biological cause of the odor. It is best not to try treating this problem yourself, and especially not with commercially available detergents, as these could cause further damage to your AC system, or prove to be hazardous to your health if inhaled.

Something Sweet

If your AC system emits a sweet smell, you need to have it checked out as a matter of priority. This sickly smell is most likely caused by a poisonous liquid ethylene glycol, also known as antifreeze. This odor is caused by a leak either in the heater core, pipe or hose, coolant housing unit, or radiator.

In this case, prevention is preferred before having to repair a leak in the system. The most effective way of avoiding this sort of smell, is to have your vehicle serviced frequently, and the AC system checked thoroughly.

Unfortunately, should you be experiencing the sweet emissions of antifreeze, the only solution will be an extensive repair job.

At the end of the day, if you are smelling something that leaves you feeling off-color, you are going to want it eliminated – fast. By having your car serviced on an on-going basis you will reduce the chances of a smell setting in. If one does take residency in your car AC, then take care of it quickly and permanently by having your car checked by a reliable and reputable mechanic at Foreign Affairs Motorsport as soon as possible.

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