Why Does My Car AC Smell?

Your car AC smells might be telling you about something pretty important. AC smells might be caused by something as simple as an excess of moisture, but it could also be cluing you in on leaks. A smell from your air conditioning might be an early sign that there's a coolant leak or even a gas leak happening under the hood.

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Rachel Bodine graduated from college with a BA in English. She has since worked as a Feature Writer in the insurance industry and gained a deep knowledge of state and countrywide insurance laws and rates. Her research and writing focus on helping readers understand their insurance coverage and how to find savings. Her expert advice on insurance has been featured on sites like PhotoEnforced, All...

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Written by Rachel Bodine
Insurance Feature Writer Rachel Bodine

Leslie Kasperowicz holds a BA in Social Sciences from the University of Winnipeg. She spent several years as a Farmers Insurance CSR, gaining a solid understanding of insurance products including home, life, auto, and commercial and working directly with insurance customers to understand their needs. She has since used that knowledge in her more than ten years as a writer, largely in the insurance...

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Reviewed by Leslie Kasperowicz
Farmers CSR for 4 Years Leslie Kasperowicz

UPDATED: Mar 11, 2022

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What You Should Know

  • If AC smells of mold or mildew the smell is most likely caused by growth of bacteria or fungi
  • If AC smells of gasoline there is a chance you have a gas leak, and should be checked right away
  • If AC smells of syrup this could mean your AC cooling system is leaking coolant into the AC ducts

Have you ever turned on your car’s air conditioning and been blasted with a foul odor rather than fresh cold air? Unfortunately, this is a common problem with a variety of potential causes. This unpleasant smell could be coming from the AC unit itself or it could be blowing in from somewhere else in or around the car.

This leaves you asking the question, why does my car AC smell? 

In this article, we’ll cover the most common bad smells that could come from your car’s air conditioner and how to fix them.

Depending on your coverage and the cause of the smell, getting your AC fixed might be covered by your auto insurance. You can find the best auto insurance rates with our free quote comparison tool right now.

The AC Smells of Mold or Mildew

One of the most common bad odors that develops from a car AC is a stale, moldy smell. This smell is most likely caused by the growth of bacteria or fungi.

Microorganisms love to grow behind your dashboard on the evaporator, a prime location for their smell to be blown into your car through the air conditioner vents. With regular use, dirt and dust can gather in the air intake vent for the AC. This buildup of debris decreases airflow and traps moisture on your AC evaporator. 

This wet environment of trapped gunk is perfect for bacteria, mold, and mildew to fester.

How Do I Fix It?

As soon as you notice the problem:

  • Avoid frequently using your car air conditioner on a high setting, as this can cause excess water to drip into the unit and encourage more germs to grow.
  • Let the fan run by itself, as this will dry off the coils in the AC unit and stop the drip.

Check your AC evaporator drain tube for clogs:

  • If you do not see water dripping from the bottom of your car when your AC is running, it is a good sign that your AC drain hole could be clogged.
  • Locate your car’s AC drain using your owner’s manual. If it is under the car, have a mechanic check it for you to avoid any gross or dangerous mishaps.
  • If your car’s drain hole is accessible, check to see if it is full of leaves, mud, or other foreign substances.
  • You can try to manually dislodge clogs with a long piece of wire. Bend the wire on one end to form a small hook. Carefully insert the wire hook into the drain hole and pull out any debris.
  • Make sure to disinfect the drain after clearing blockages to kill any bacteria that may be contributing to the problem.

Disinfect your AC evaporator:

  • You can flush out bacteria that may be living on your evaporator or in your air ducts through the air intake under the hood.
  • You can use a specialized vent and duct cleaner or just a household disinfectant spray.

It’s worth noting that professionals will be able to do a much more thorough job clearing and disinfecting your evaporator using commercial-grade disinfectants. If you aren’t very familiar with the inner workings of your car’s air conditioner, it may be better to leave this job to the professionals.

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The AC Smells of Gasoline

Smelling gasoline when you’re not actively pumping gas can be worrisome and even frightening. If the AC is pumping in the smell, there is a chance that you have a gas leak. The smell of gas is being sucked in through the air intake and pumped into your car through the AC.

How Do I Fix It?

As soon as you notice the problem:

  • Shut off your car. Stopping the engine can help prevent any issues related to the gas leak from getting worse.

Repair any leaks:

  • Repairing a gas leak is a job best left to a mechanic.
  • That being said, there are a few different places a leak could be originating. The fuel pressure regulator, the fuel injector, the exhaust pipes, and the muffler could all have issues that result in gas leaks.

The AC Smells of  Something Burning

How you should react to a burning smell depends on what kind of burning you detect. There are many different kinds of burning smells, including oil, rubber, and plastic.

Burning Oil

A burning oil smell is probably due to an oil leak somewhere in your car. When your engine is running, it generates a lot of heat. If leaky oil hits the hot machinery under the hood, it generates a noxious burning smell that your AC then blows in on you.

Burning Rubber

A burning rubber smell likely comes from the AC itself. The AC compressor, the compressor clutch, or a pulley could be potential sources. If these parts are misaligned, it could cause a belt to drag. This friction can cause a burning rubber smell.

Burning Plastic

There are a large number of reasons why you could be smelling burning plastic. It could be something as low-risk as excessive dust in your air vents. Or, it could be something as problematic as electrical shorts or burning wires.

How Do I Fix It?

Because there are so many different reasons why something could smell like burning, it’s best to get the advice of a professional. Shutting off the car is always a good idea when you think something could be wrong with the engine or oil.

The AC Smells of  Syrup

A sickly sweet, almost syrupy smell is a particularly odd thing to encounter when turning on your AC. Luckily, it has an easily diagnosable origin: antifreeze. The sweet smell comes from the ethylene glycol in antifreeze, a common component of engine coolant. If you can smell it when turning on your AC, your cooling system is likely leaking coolant into the AC ducts. So, how often should antifreeze be changed? It depends, but if you detect this smell, it’s time to change out your antifreeze. 

How Do I Fix It?

As soon as you notice the problem:

  • Check for a slimy film on the inside of your windows and windshield. This is another indicator that there is coolant liquid being aerosolized through your AC.
  • Have your AC unit checked immediately. In addition to leaks being damaging to your car, antifreeze is toxic and should not be ingested in liquid or gaseous forms. In other words, you should not be breathing it in!

Have your cooling system checked for leaks and damage:

  • A leak could be coming from the heater core, coolant housing unit, cooling system pipes, or radiator. 
  • Installing a new heater core or radiator can be difficult, costly, and dangerous when done incorrectly. Consider taking this job to a mechanic or service center.

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The AC Smells Stale

If your air conditioner is blowing out stale, stuffy air, it could be a simple problem with a simple solution. According to CarsDirect , there is a good chance that your air filters are dirty and need to be cleaned.

With regular use, air filters will pick up dust, dirt, moisture, and other pollutants from the air that moves through your AC vents. If they are full, they will not work as well and may start to generate a stale, dusty smell.

How Do I Fix It?

The simple solution is just to replace the air filters. Consider incorporating the task of cleaning the AC unit air filter into regular maintenance.

The AC Smells of  Vinegar

The strong smell of vinegar is undeniable, but the root cause may not be so straightforward. There are several reasons why your air conditioner may be blowing out a sour, vinegar smell. These include:

  • Mold
  • Ozone emissions
  • Leaking battery acid

How Do I Fix It?

First, try using a vent and duct cleaning spray or household disinfectant spray to clean your air ducts. This can kill any bacteria or mold living in the vents of your AC unit.

If the problem persists, take your car to a service center. There may be a more serious and dangerous problem that should be assessed by a professional.

The AC Smells of  Chloroform

The smell of chloroform is a difficult smell to identify if you aren’t familiar with the chemical. Similar to acetone (think: nail polish remover), a chloroform smell could be indicative of a refrigerant leak.

Freon, the chemical commonly used in AC evaporators as refrigerant, smells like chloroform mixed with something sweet. If refrigerant leaks into a part of the evaporator that blows air into the vents, you will smell it coming from your air conditioning unit.

Another common indicator of a refrigerant leak is a lack of airflow from the AC vents. If the AC compressor is leaking refrigerant, it can cause the AC evaporator fans to become sticky and trap dirt. This will restrict their ability to move and create airflow. If you hear the fans running but don’t feel any air moving, this could be the reason. Looking for the average car air conditioner compressor repair cost? We’ve got you covered. 

How Do I Fix It?

It’s difficult to access the AC evaporator to fix any leaks because it’s hidden under the instrument panel. The best solution is to bring your car to a mechanic so they can diagnose and fix the issue.

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Protect Yourself and Your Vehicle

It can be worrisome to be caught by surprise with a foul smell blasting from your car’s air conditioner. But, if you are able to identify the potential problem early, you can prevent further damage and keep both yourself and your car healthy. Our experts can also provide helpful details on when to get an oil change or the common symptoms of bad shock absorbers and symptoms of bad brake pads.

Insurance is a necessary part of car ownership, and it doesn’t have to be as confusing as identifying a mystery smell from your AC. With our help, you can compare rates from all of the top insurance providers and find the most competitive plans that fit your budget.

We’re your one-stop shop for auto insurance comparison: less time, less hassle, and free! Get started with your free quotes today.

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