Why Does My Cars Air Conditioning Smell Bad?

Air conditioning is great, especially in a hot and humid climate like Queensland. In summer, your car becomes an oasis of cool, temperature controlled bliss. But, slowly over time (or sometimes all at once), a bad smell can begin to seep through your air conditioning system. Not only is a bad smell off-putting, it can be damaging to your health and/or your car. Find out why your air conditioning smells, and what you can do to fix it.

What causes smells in your air conditioning system?

There are a number of different reasons why your air conditioning system may be producing a bad smell. Some of the common reasons include:

Dirty Air Filters

One of the most common causes of a bad smell from your air conditioning is dirty air filters. These filters work to scrub the air of water, dirt, bacteria and other pollutants before entering into your air conditioning system. Over time, these filters begin to fill up with pollutants and need to be replaced. If the filter is not replaced at the appropriate service interval, it may lead to an unpleasant smell from your air conditioner every time you use it.

A Bacteria Build Up

Despite the best efforts of your air filters, dirt and bacteria can begin to build up inside of your vehicle’s air conditioning system over time. This build up causes an unpleasant and musty smell to circulate through your vehicle’s vents and into your car. This build up can also be caused by an extended period of inactivity by your vehicle’s air conditioning system, allowing a perfect environment for bacteria to breed.

A Fluid Leak

Your car uses a number of different fluids such as coolant and oil to run effectively and stay healthy. When one of these fluids leaks and finds its way into your car’s AC system, it may begin to give off an unpleasant smell. Not only does it smell, it may be indicative of a bigger issue in your car that may be causing damage to your engine. If your air conditioning begins to smell sweet, it may be the toxic antifreeze in your coolant (also known as ethylene glycol) leaking into the system. You should have this issue addressed immediately as it can damage your eyes and respiratory tract.


Your air conditioner pulls moisture from air as part of the cooling process. This allows the air to be pleasant and dehumidified inside of your car, however this moisture has to go somewhere during this process. Water droplets can form on the evaporator core of your air conditioning system, creating a damp environment that is a perfect breeding ground for mildew. This mildew releases an unpleasant smell which is then sucked up by your air conditioning unit. If your air conditioning unit is dripping water but you’re unsure of the cause, consider reading our blog post : Why Does My Air Conditioner Drip Water?.

What can you do to prevent smells in your air conditioning system?

Regular maintenance of your air conditioning system is the best way to ensure it stays in working order without any bad smells. Replacing filters, fixing leaks and flushing your air conditioning system are great ways to keep your air conditioning servicing up to date.

If you’re ready to book in for an air conditioning service with a team of highly skilled mechanics, contact us at Australian mechanical today on 07 3356 1538.

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