Bad Smell From Car AC: How to Fix it?

Your vehicle’s air conditioning system is an essential component in having a pleasurable driving experience, especially during the summer season. There’s no better driving experience than controlling the air conditioner in your vehicle during summertime. Unfortunately, overuse of the car ac will wreak havoc on the air conditioning system and cause a bad smell from the car ac.

If you have ever turned on your car ac in full blast during a hot afternoon and your car ac smells like a rotten egg or emits some terrible smells, then you know exactly what we’re discussing here. This smell can come in various ways, and it has been described as a car smell like gas, burnt plastic, rotten eggs, dirty socks, musty, and fishy, to name a few – and it can even be accompanied by dizziness and headache. You wouldn’t want to experience such. Let’s talk about why this foul smell occurs and how to remove bad smells from car ac.

What causes car ac to smell bad?

Your car ac does not create cold air. Sounds surprising, right? Now, how comes about the cold air in your vehicle? What the ac system does is take moisture and heat out of the outside air, which makes the air inside the car much colder. The AC unit coils condense the air’s heat and moisture, removing humidity before sending the cold air inside your car through the AC vents.

how do you get rid of smell in car ac

As this air conditioning is much colder than the surrounding air, the air entering into the unit can create moisture that surrounds the condensing components in your car air conditioning system, which forms a small stream of water that drips out of the vehicle through the AC drain pipe. However, if the moisture fails to find its way out of the car by evaporation or drainage, the water stream will drip into the AC unit surrounding the coils. This will result in moisture inside the car. Let’s look at several other reasons why aircon smells musty.

Gas leak: If your car smells like gas, whenever you turn on your car ac, you probably have a gas leak somewhere in your ac system. When you switch on your ac, the gas smell will transpose in the air condition. That is to say, and the air conditioner will be taking both fresh air and gas smell instead of only fresh air. This can cause a bad smell coming from ac vent in the car and should be traced and fixed on time to prevent the unpleasant smell.

Dirty Cabin air filter:  Your air filters can also cause a musty smell coming out when you turn on your car ac. If the AC filter clogs, it will attract dust, dirt, and other harmful pollutants. This can cause an unpleasant smell inside your car, mainly when you turn on your car ac.

car ac smells bad when first turned on

Coolant leak:  In as much as car bad smell from your ac vent is of great concern, if your vehicle cooling system smells sweet, it is an indication of a problem too, and you should check your cooling system ASAP. The sweet smell results from an antifreeze leak or liquid ethylene glycol. The antifreeze leak can come from the radiator, coolant housing unit, hose or pipe, or heater core.

Bacteria and Mold: Bacteria and Mold is the primary reason why bad smell comes from car ac. A rotten egg smell, musty, fishy, or gas smell can be due to mold and bacteria growth in your vehicle. As your vehicle ages, fungi, mold, bacteria, and microorganisms start to grow. These micro-organisms and bacteria usually grow around the evaporator at the back of your dashboard panel. The growth forms a terrible odor when you turn on your car ac. If you do not use your car ac for long, it can also cause mold and bacteria to grow. Often blasting your air conditioner and leaving it at MAX also cause the growth of fungi, bacteria, molds, and micro-organisms – since the AC drips excess water when on MAX.

How do you fix the bad smell from the car ac?

The ideal way of fixing car ac smell is finding and fixing the cause of the odor. As we mentioned in the few paragraphs above, foul odor from vehicle air conditioners can result from gas leaks, coolant leaks, dirty air filters, and mold/bacteria – the primary cause.

The first thing you want to do when removing the unpleasant odor from car ac is to check the air filter. If the air filter is the culprit, you can remove the bad smell by cleaning or replacing the old air filter. If your car ac after a changed cabin air filter still smells, you may have to move to the next level. Since the primary cause of car ac terrible smell is due to mold and bacteria, let me walk you through how to get rid of bad smell from car ac caused by mold and bacteria in the AC system.

Step 1. Turn off your ignition and locate the AC vents: Turn off your car engine and locate your car ac vents and all the ducts in the car. Go ahead and spray clean air duct treatment into those vents. Ensure you spray the treatment with a straw attached to the spray container. Don’t forget to spray the treatment on the passenger side too.

Step 2. Turn on your engine: Now, turn on your engine and set the AC system to a MAX fan. Set the temp to the lowest, turn on the AC and set it on maximum recycling settings. You have to locate the recycling intake duct on the passenger side, near the floor. The intake duct is very low; you won’t normally see it. Locate it and spray half of the can into it, and you will see it sucking right into the system.

Step 3. Change your AC settings to fresh air: Now, change your settings to fresh air, take it off from max settings. You want fresh air coming into the system from the outside. Close your doors and go out and locate the fresh air grill on your vehicle. It’s located right below the windscreen, close to the hood. Insert the straw into those drills and do a couple of shots in them. You may need to lift the hood in some vehicles to access those grills easily.

Now, go ahead and shut off your car, open the doors and allow fresh air to get into the cars. It can take you less than three minutes at most. At least I forget; I also recommend using Ultra shield air conditioner treatment for taking out foul odor from your AC unit. These treatments can also get rid of cockroaches in your car.

How to Fix Smelly AC in Your Car Like the Pro in 3 Minutes YouTube Video


Q: What does a Freon leak smell like?

Freon typically passes through copper coils in the air conditioning unit; over time, these coils can damage and cause air conditioner antifreeze leaks. Freon leak smells somehow like sweet and chloroform.

Q: Can leaking Freon make you sick?

Freon has a significant impact on the air conditioning system and human health. Freon leak can cause nausea and vomiting, headache, difficulty breathing, coughing, and eye and skin irritation.

Q: Why does my AC smell like sewage?

The sewage smell from your AC vents usually indicates a ruptured or backup sewer line vent pipe around the ductwork. A single bit of methane from the backup line will fill your AC with a sewage smell.

Q: Is a smelly air conditioner dangerous?

A smelly air conditioner can be dangerous to human health in various forms, ranging from none to discomfort, and to more serious effects. Some AC chemicals can cause throat, lung, eye, or nose irritation.

Q: What does it mean when your car ac smells bad?

Bad smell from home or car AC results from fungi, mold, and bacteria growth around the copper coils in your evaporator unit.

Final word:

If you are still reading till this point, it means you have experienced or want to get rid of bad smell from car ac. And I believed we had cleared your head from wondering, “why does my car ac smell like pee?”.

In case you skimmed through the paragraphs above, foul odor from your AC vent is usually caused by a gas leak, dirty air filter, antifreeze leak, and mainly as a result of mold and bacteria. However, the step on how to clean unpleasant smells from your AC vent is a temporary fix. I recommend taking your car to an HVAC expert; suppose the smell comes back soon.

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Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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