Why Does My Car AC Smell Like Rotten Eggs?

The presence of a foul odor resembling rotten eggs in your car's AC system may have several potential causes.

These include a malfunctioning catalytic converter, a damaged fuel compressor sensor, a leaking car battery, the use of old transmission fluid, or the decay of organic substances within the vehicle.

Is there a problem with my car's catalytic converter causing the AC to smell like rotten eggs?

One possible cause of a foul odor resembling rotten eggs in a vehicle is a failing catalytic converter. The primary purpose of the catalytic converter is to transform harmful gases into less harmful substances. However, when the catalytic converter fails or becomes contaminated, it is unable to process sulfur compounds in the exhaust gases, resulting in the characteristic sulfuric or rotten egg smell. If you detect this odor in your car, it is likely an indication of a broken or malfunctioning catalytic converter.

Read also Why Does the AC Come On with Heat in a Car?

Why does my catalytic converter smell rotten egg?

The fuel pressure regulator is a crucial component in your car's engine as it is responsible for regulating the flow of fuel. If this regulator, along with the fuel sensor and filter, becomes broken or faulty, it can cause the catalytic converter to be flooded with oil. As a result, the catalytic converter will eventually fail, leading to a noticeable smell of rotten eggs in your car.

If you notice your car emitting a rotten egg smell, it is indicative of a problem with the fuel pressure regulator or other related components. It is important to address this issue promptly to prevent further damage to your vehicle.

What happens if a catalytic converter is clogged?

If the catalytic converter in your car is clogged, it can cause overheating and result in the burning of accumulated byproducts. This can also lead to the release of hazardous gases into your car. If the catalytic converter is the culprit, you will likely notice the smell of sulfur in your car shortly after starting the engine.

What is a bad catalytic converter code?

The P0420 code is one of the most frequently encountered trouble codes that indicates a malfunctioning catalytic converter.

If you notice a delay in acceleration or a loss of power when driving uphill, despite all other components such as spark plugs, filters, and sensors being in good condition, it is likely that the catalytic converter is faulty.

Why does my engine smell rotten eggs?

A catalytic converter is an essential component that helps to convert the harmful chemicals emitted from the engine into harmless elements. If the converter becomes clogged or is no longer able to effectively facilitate chemical reactions, a rotten egg smell may become noticeable due to the emissions from the exhaust system.

If your car smells like rotten eggs, it is likely due to the malfunction or inability of the catalytic converter to properly carry out its chemical conversion process. This issue should be addressed promptly in order to ensure the car's emissions are within acceptable and safe levels.

Could a sulfur-like smell in the AC be an indicator of a failing battery?

If there is a foul odor resembling rotten eggs coming from your AC system, it is possible that there is a battery leakage. Leaking batteries emit a sulfur smell, which can sometimes be reminiscent of the scent of rotten eggs.

See also Why Does My Car's AC Smell Burnt?

Why does my AC smell like sulfur?

A sulfur smell often indicates a gas leak, which can be a serious issue. If you detect this odor when you turn on your air conditioning, it is important to immediately switch it off and seek assistance from a professional heating and cooling specialist.

On the other hand, a sweet or chemical smell from your AC may suggest a refrigerant leak. It is advisable to address this problem promptly and consult with an expert to resolve the issue.

Why does my air conditioner smell?

Burning or electrical odors in your air conditioning system can be a sign of mechanical issues with the compressor or fan, electrical component failure, or wiring problems. It is important to note that these odors can be harmful due to the chemicals and metals used in these components.

If you detect any of these smells, it is recommended to address the issue promptly to avoid further damage and potential health risks.

Why does my AC smell like a fried circuit board?

A potential cause of a burning smell in your air conditioner could be a malfunctioning circuit board, power wire, fan, or compressor. The presence of a burning odor indicates that one of these components is actually burning. It is advisable to turn off your air conditioner immediately and seek assistance from a professional in air conditioning services. It is important to avoid attempting to resolve the issue yourself as it could potentially be hazardous.

The article "7 Types of Air Conditioner Smells and What Each Means" available on guysac.com provides further insights into different types of smells that may emanate from your air conditioner and their corresponding causes.

Why does my car battery smell Rotten?

One of the early indicators of a battery issue is the presence of a rotten egg smell. Traditional acid lead automotive batteries contain a combination of water and sulfuric acid. Over time, some of the acid and water may evaporate from the battery, disrupting the mixture.

This can result in the emission of a foul odor resembling rotten eggs. If you notice this smell, it may be a sign of a malfunctioning or deteriorating battery.

In such cases, it is advisable to seek the assistance of a professional mechanic to diagnose and address the problem promptly.

Is the AC compressor leaking refrigerant, leading to the unpleasant odor in my car's AC?

One potential cause for a malfunctioning car air conditioner is a leak in the compressor shaft seal. This leakage results in a loss of refrigerant which subsequently impairs the AC's functionality. Other indications of a compressor shaft seal leak may include audible hissing or bubbling sounds upon activating the AC, as well as the presence of fluid leaks near the front of the vehicle.

Read more: Why Does My Car AC Get Hot When Idling?

How do I know if my AC unit has a refrigerant leak?

There are several signs that may suggest a refrigerant leak in your AC unit. One indication is a higher electric bill, as a refrigerant leak can cause the unit to work harder. If you notice an unexpected increase in your electric bill, it is possible that your air conditioner has a refrigerant leak.

Why is my AC leaking?

If the compressor clutch of your AC starts to fail, one possible indication is leaking refrigerant. This can occur when the clutch is not functioning properly, causing the front seal to develop leaks. As a result, the car AC refrigerant will escape through small openings, compromising the cooling capacity. Determining the severity of the leak will accurately reflect the extent of the cooling impairment.

How do you know if a compressor is leaking?

One of the signs of a bad A/C compressor is the presence of a hissing noise or bubbles when the compressor is sprayed with soapy water, which indicates a refrigerant leak.

Another indication of a faulty compressor is excessive cycling on and off, which can be caused by a bad clutch, a leak, or internal wear.

These are some signs to look out for in a compressor that is not functioning properly according to AutoZone.

What causes AC refrigerant & Freon leaks?

There are several common causes of AC refrigerant or Freon leaks including improper installation, metal erosion, and factory defects. Improper installment, where certain components are not properly secured, can lead to leaks. Metal erosion can also cause small holes to form, resulting in refrigerant leakage. Additionally, if an AC unit is defective from the factory, leaks may occur over time.

Could a faulty PCV valve be causing the rotten egg smell to come from my car's AC system?

A breather element, when the PCV valve starts to fail, can become contaminated with hydrocarbons and oil. This is a result of the increased pressure that builds up in the crankcase, causing water vapor to be pushed through the breather element.

Related: Why Is My Car AC Vent Blowing Smoke?

Can a bad PCV valve cause a car to run?

If your vehicle is displaying symptoms of a faulty PCV valve, it should still be able to function, but it is important to address this issue in a timely manner. There are two distinct types of PCV valve symptoms, with one of the most common being a noticeable whistling or hissing sound originating from the engine.

It is crucial to be aware of the symptoms of a bad PCV valve and take appropriate action before any further complications arise. This includes addressing any whistling or hissing sounds emanating from the engine, as they may indicate a malfunctioning PCV valve.

Could a clogged PCV valve cause blue smoke?

If the PCV system becomes clogged, it could potentially lead to an increase in pressure, resulting in gasket leakage.

In regards to the question about blue smoke from the exhaust occurring only at idle, it is possible that a faulty PCV valve could contribute to this issue. This could be due to a restriction within the PCV system that creates excessive pressure in the crankcase.

If you suspect a faulty PCV valve, there are methods available to test it yourself.

How do you know if a PCV valve is faulty?

A faulty PCV valve can exhibit several common signs, such as increased oil consumption, oil leakage, a clogged breather filter, and diminished overall performance.

The purpose of the positive crankcase ventilation (PCV) valve is to remove gas from the engine's crankcase. This valve then channels the gas back into the combustion chambers through the intake manifold.

When the PCV valve starts malfunctioning, it can result in symptoms like excessive oil usage, oil leaks, a blocked breather filter, and a decline in the engine's performance.

Can a PCV valve cause oil to leak?

If you detect the smell of gasoline in the oil or observe fumes passing through the valve, it is likely that the piston rings are worn and allowing fuel to pass through. This can occur in a rich mixture scenario.

Regarding the question of whether a stuck or closed PCV valve can cause oil leakage into the intake manifold, the answer is yes.

If you are experiencing symptoms of a malfunctioning PCV valve, such as excessive oil consumption or increased pressure in the crankcase, you can test the PCV valve yourself. Detailed instructions on how to do so can be found at axleaddict.com.

Is there a chance that a blocked condensate drain line is causing the AC in my car to emit a sulfur smell?

Yes, it is recommended that an AC condensate line should not directly connect to sewage. This can result in the entry of sewage air into your AC system. To prevent this, many plumbers install a P-trap. The purpose of a P-trap is to prevent the introduction of air or water back into the system. If your AC system lacks a P-trap, it is important to have one installed promptly.

See also Why Is Fog Coming Out of My Car AC?

How do I know if my AC condensate line is clogged?

It is advisable to routinely inspect the AC condensate line when replacing the air conditioner's filter. Regular monitoring of the AC drain lines makes it easier to address any clogs that may occur. If there is an accumulation of excessive water in the drain pan, it could indicate a clogged AC drain line.

If you suspect that your AC drain line is clogged, you can find out the possible causes and learn how to fix it on HVAC.com.

Can a clogged AC drain line cause a complete system failure?

If the dirt, mold, and mildew in your HVAC system are not cleaned, it can lead to a clogged condensate drain line. This could potentially cause your entire system to fail, so it is important to know how to keep the line clean and what steps to take if you suspect a clog. To locate the condensate line, look for a pipe, commonly made of PVC, that drains outside your HVAC system.

If your AC drain line is clogged, it is crucial to understand the reasons behind it and how to resolve the issue.

Why is my AC condensate drain blocked?

The accumulation of debris in the AC coil can be washed away as condensate drains out. However, as time passes, this debris can get stuck in the condensate drain line, leading to blockages. To prevent this, HVAC technicians often examine and remove debris from the AC condensate drain as part of your yearly maintenance check-up.

What is an AC drain line?

The AC drain line is responsible for carrying water and debris from the condensate drain pan beneath the evaporator coil. Its purpose is to ensure proper drainage of the condensation from the unit either to a drain or outdoors.

If the AC drain line becomes clogged, it can cause issues with the system's functionality.

Could the smell in my car's AC be related to a fuel leak or an issue with the fuel injectors?

There are several potential causes for the smell of fuel in a car's AC system. One possible reason is a malfunctioning fuel line, which can hinder the transportation of fuel from the tank to the engine. Another cause could be a damaged or malfunctioning pressure regulator. Additionally, a gas leak or issues with the gas cap could also contribute to the smell of fuel in the AC. Lastly, loose spark plugs may be another factor to consider.

Read more: Why Is Half of My Car's AC Blowing Hot Air?

Why does my car smell like gas when the AC is on?

If the canister has become worn down over time, become damaged from prolonged use, or has been improperly installed, it can result in gas fumes escaping through compromised vents or seals. This can lead to a noticeable smell of gas when the car's air conditioning is running. Another possible explanation for this issue is...

Why does my catalytic converter smell like gas?

Exhaust fumes are a byproduct of the combustion of gas in your vehicle's engine, particularly when you accelerate. The purpose of the exhaust pipe is to expel these fumes away from your car. The catalytic converter in your vehicle is responsible for filtering the exhaust and reducing its odor. Therefore, if you detect a smell of gas, it may signal an issue with your car and should be addressed promptly.

Why does my air conditioner smell bad?

As a car ages, bacteria, mold, fungi, and micro-organisms have the potential to develop. Typically, the growth of these bacteria occurs in the area behind the dash panel on the evaporator. Consequently, an unpleasant odor can be emitted from the air conditioner unit. Additionally, infrequent usage of the air conditioner can contribute to bacteria growth.

What causes a gas injector to leak?

The leakage of fuel from your car's injector can occur due to leaks from the o-ring seal or the rubber.

Every type of injector contains a rubber seal positioned at the bottom and an o-ring positioned at the top, both of which play crucial roles in maintaining a proper seal.

Is the odor in my car's AC system indicative of a coolant leak or radiator problem?

If you happen to detect a sweet smell coming from your car's cooling system, it is highly advisable to promptly have the unit examined. This distinctive scent is commonly attributed to the presence of ethylene glycol or antifreeze, which can be toxic. The source of the smell can typically be traced back to a leak within the cooling system, which may originate from various components such as the heater core, pipes or hoses, coolant housing unit, or the radiator.

Related: Why Isn't My Car's AC Blowing Hard?

Why does my car's AC smell like coolant?

A common cause of a coolant smell emanating from your car's AC vents is a leak in the heater core. The heater core is an integral component of your car's cooling system, and various parts are interlinked. When there is a leak in the heater core, you may notice a distinct coolant smell when you activate your car's AC.

Why does my radiator smell sweet?

The sweet smell in your car may be caused by a leak of antifreeze or liquid ethylene glycol, which can originate from various parts such as the radiator, coolant housing unit, hose or pipe, or heater core.

If you are experiencing a bad smell from your car's AC, there are suggested remedies available to address the issue.

Why does my AC vent smell bad?

There are several common causes for a foul odor coming from your AC vent, such as a gas leak, dirty air filter, antifreeze leak, or the presence of mold and bacteria. However, it's important to note that the steps to cleaning these smells are only a temporary solution. If you're experiencing a bad smell from your car AC, there are methods you can try to alleviate the issue.

One potential cause for an unpleasant odor is a gas leak, which can emit a foul smell. Another possibility is a dirty air filter, which can cause stale air to circulate, creating an unpleasant scent. An antifreeze leak can also lead to a bad smell, as the liquid has a distinct odor. Additionally, mold and bacteria can thrive in the moist environment of the AC system, resulting in an unpleasant odor.

While there are steps you can take to temporarily clean the AC vent and reduce the bad smell, it's important to note that this is not a permanent fix. To address the issue more comprehensively, it is recommended to seek professional assistance from a mechanic who can diagnose and repair the root cause of the odor.

How do I know if my coolant is leaking?

One of the most noticeable signs of a coolant leak is the presence of a pool of coolant underneath the vehicle. It may also be observed as dripping from a visible leak or from an area within the car. This is typically caused by a leak in the radiator or a damaged pipe.

If you detect a coolant smell coming from the air conditioning system, there are seven common causes that may be responsible.

Could a dirty or contaminated engine air filter be causing the rotten egg smell in my car's AC?

Consider replacing the cabin air filter to eliminate the trapped odor. The cabin filter, typically located in the glove box, is responsible for filtering emissions that may enter the interior of your vehicle.

Read also Why Are My Car AC Lines Hot?

Why does my Car Smell rotten eggs?

Making an appointment with a reputable mechanic is advisable if you detect a foul odor resembling rotten eggs in your vehicle. This odor typically indicates a functional issue with your car, and a qualified mechanic has the necessary tools and expertise to accurately identify and resolve the problem. They will conduct a thorough inspection to determine the specific component causing the offensive smell.

If you are facing a rotten egg smell in your car, it is recommended to schedule an appointment with a trusted mechanic promptly. This unpleasant odor often indicates a functional problem with the vehicle, and a professional mechanic is equipped with the necessary tools and knowledge to effectively diagnose and address the issue. They will conduct a comprehensive inspection to identify the specific car part responsible for the offensive smell.

Why does my car smell like gas?

In rare situations, a blocked fuel filter or a damaged fuel pressure regulator may be the cause of the unpleasant smell resembling rotten eggs. However, these problems are more commonly associated with a gas smell in your car.

To rectify the issue, it is important to note that the fuel pressure sensor is a delicate component that necessitates specialized tools for calibration.

Is the issue with my car's AC related to a malfunctioning blend door or actuator?

A malfunctioning blend door actuator can result in an inadequate functioning of the air conditioning system, as it is responsible for regulating the airflow and temperature of air entering through the A/C vents and defrost vent.

Recognizable signs of a defective blend door actuator include the presence of cold air blowing from the AC, inconsistent airflow, audible clicking noises, malfunctioning defrost vents, and faulty temperature control.

Related: Why Is My AC Clicking in My Car?

How do I know if my blend door actuator is bad?

A bad blend door actuator is typically indicated by issues with the air conditioning controls in your car and the presence of unusual noises emanating from the air vents.

You might observe inconsistent temperature or airflow as well. In case you are uncertain about the signs, here is a comprehensive list of the most frequently observed indications of a faulty blend door actuator:

1. Strange sounds.

Why is my car's AC not working?

If your car's AC is not functioning properly, it is possible that the Blend Door Actuator is causing the issue. If you are unsure how to test or fix it, we can provide guidance. The blend door actuator sometimes malfunctions, which may lead to a failure in allowing heated air to enter the passenger area.

Can a faulty blend door actuator stop climate control from working?

A faulty blend door actuator can cause issues with your vehicle's climate control system, but it will not affect the overall performance of your vehicle.

If you can tolerate the inconvenience of the climate control system not functioning properly, there is no reason to refrain from driving with a faulty blend door actuator.

Why does my door actuator go bad?

The actuator relies on a series of plastic gears to control the position of the door, which can be prone to breaking. Additionally, the door position sensor can potentially malfunction, leading to issues with the actuator. Other potential causes of actuator failure include various reasons which are discussed in more detail in the article "Blend Door Actuator Symptoms - Causes and Fixes" on REREV.com.

Could a faulty heater core cause the AC to emit a foul smell like rotten eggs?

A potential source of antifreeze leaks in a car can be the radiator, coolant housing unit, hose or pipe, or heater core.

Bacterial and mold growth is a common cause of unpleasant odors emitted from car air conditioning systems. These odors can manifest as a rotten egg smell, musty odor, fishy scent, or a strong gas smell.

Check also Why Is My Car AC Leaking Water Inside?

Why does my air conditioner smell like rotten eggs?

If you detect a sulfur-like or rotten egg smell coming from your air conditioning unit, it is probable that there is a source of the odor in your home that is being circulated through the ventilation system. This smell is one of the six common odors associated with air conditioning systems and has a distinct meaning.

Why does my air conditioner smell like running car exhaust?

There should not be any reason for your air conditioner to emit a smell resembling that of a running car exhaust. However, it is worth noting that air conditioners do utilize fluids, and when these fluids become heated, they can produce an odor similar to exhaust fumes. If you are detecting such a smell, it is highly probable that there is a leak in your refrigerant line, which would require immediate attention and repair.

If you are experiencing unpleasant smells emanating from your air conditioner, it is important to address the issue promptly. In order to identify and rectify the problem, it is advisable to consult with a professional HVAC technician who can provide the necessary insight and expertise to resolve the issue.

Why does my electric heater smell?

An electrical odor in an HVAC system is often caused by issues with the motor or wiring. It is important to note that attempting to fix these components can be dangerous and may result in serious injuries.

In the autumn, when the heater first starts running, it is not uncommon for a burning odor to be emitted. This odor can often have an electrical or dusty smell.

Source: "5 Common HVAC Odors (And What Causes Them)" - Compact Appliance.

Can a leaking heater core cause overheating?

A low coolant level resulting from a heater core leak can cause the engine to overheat and potentially suffer damage. Additionally, a blocked heater core can restrict the flow of coolant, leading to overheating. It is important to be aware of these symptoms to prevent any potential problems with the heater core.

Is the odor in my car's AC system caused by mold or bacterial growth in the evaporator or ventilation system?

The AC in a car can emit a moldy odor due to the presence of mold growth in the evaporator coil or fins. The primary purpose of the evaporator is to remove heat and humidity, but it can become humid and obstructed by mold or fungi.

In addition, the condenser fins may sustain damage, which can result in increased moisture being trapped.

The accumulation of dirt, dust, and debris in the under-hood air intake vent can also contribute to water and moisture becoming trapped on the AC evaporator and in the evaporator case. This scenario provides an ideal environment for the growth of germs, mold, mildew, and other microorganisms.

Why does my car air conditioner smell?

The air conditioning system in your vehicle has the capability to condition air from outside or recirculate the air that's already inside. If there is a strange odor near or inside your car, the air conditioner can distribute that smell through the vents. This can result in the odor being present when you use the air conditioning system.

The presence of odor in your car's air conditioning system is a common issue that many drivers experience. The odor can be caused by a variety of factors such as mold, mildew, bacteria, or even a clogged cabin air filter. Identifying and resolving the underlying cause is important to eliminate the unpleasant smell and maintain a comfortable driving experience.

If you are experiencing a foul odor coming from your car's air conditioning system, it is advisable to have it inspected and serviced by a professional. They will be able to identify the source of the odor and recommend the appropriate course of action to resolve the issue and ensure the air inside your vehicle remains fresh and clean.

Why does my AC smell like mold?

If you notice an unpleasant, musty odor when you use your car's air conditioning, there's no need to suffer through it. The cause of this odor is likely a buildup of mold and mildew in your AC system, which can occur naturally due to moisture. To address this issue, follow these steps to eliminate the odor from your car's air conditioner.

First, start by turning off your car's engine and opening all the windows. Next, locate the air intake vent for the AC system, which is usually found near the windshield or on the outside of the car. Remove any debris or leaves that may be blocking the vent, using a vacuum cleaner or a brush. Then, spray an odor-neutralizing cleaner directly into the intake vent. Allow the cleaner to sit for a few minutes before starting your car and turning on the AC system.

Once you've turned on the AC system, allow it to run for about 10 minutes on the highest fan and coldest temperature settings. This will help distribute the cleaner throughout the system and eliminate any remaining odors. After this, lower the fan speed to the lowest setting and repeat the process for another 10 minutes. Finally, close the windows and let the AC system run on its regular settings for another 10 minutes to ensure that any lingering odors are completely eliminated.

By following these steps, you can effectively remove the odor from your car's air conditioner and enjoy fresh, clean air while driving.

Why does my car smell like mold?

Mold and bacteria can begin to grow in car vents if they are not regularly cleaned. This can lead to unpleasant odors and potentially make individuals sick. It is important to inspect and clean the vents if a musty smell is detected.

Source: Musty Smell From Car AC: Causes and How To Get Rid Of It - Mechanic Base

What is mold in my car's air conditioning unit?

Mold is a type of fungus that has the ability to grow in various environments, including within the air conditioning unit of your vehicle. The presence of mold in your car's AC unit is often concealed within the depths of the dashboard, making it challenging to identify during a pre-purchase vehicle inspection.

Could the smell in my car's AC be the result of a malfunctioning air freshener or deodorizer?

The musty smell emanating from a car's AC system can be attributed to several possible causes. These can include a dirty or worn-out cabin air filter, the presence of mold in the vents, a moldy evaporator coil or fins, excessive condensation, or the accumulation of dead organic material.

Why does my car AC smell bad?

A bad smell coming from the AC vent in your car can occur when there is a problem with your AC system, and it is important to address and resolve this issue promptly to prevent any unpleasant odors.

One potential cause of a musty smell is a dirty cabin air filter. If the air filter becomes clogged, it can attract dust, dirt, and other harmful pollutants, leading to an unpleasant odor when the AC is turned on.

To fix the bad smell from your car's AC system, it is recommended to trace the source of the odor and take appropriate measures to resolve it. This may involve cleaning or replacing the cabin air filter and ensuring that the AC system is properly maintained.

How to remove odor from car AC?

When dealing with an unpleasant odor in the car AC, the initial step should be to inspect the air filter. If the air filter is the source of the problem, addressing the issue can be done by cleaning or replacing the existing filter. In the event that the foul smell persists even after replacing the cabin air filter, further actions may be necessary to resolve the problem.

Why does my car smell like water?

According to Jake Fisher, the Senior Director of Auto Testing at Consumer Reports, the odor you are likely detecting is caused by condensation from the evaporator in your heating and cooling system. This condensation accumulates and can create a musty smell if it remains for an extended period of time.

If you are looking to eliminate the unpleasant odor from your car's air conditioner, Consumer Reports provides some suggestions on how to do so.

Is there a chance that the odor in my car's AC is being caused by a dead animal trapped in the ventilation system?

In some cases, birds, rodents, insects, lizards, and other small animals may seek refuge or build nests in your ducts. Unfortunately, they can become trapped and perish, resulting in an unpleasant odor that should be addressed promptly. If you have identified the presence of a deceased animal in your vent or an accessible duct, it may be possible for you to safely remove the animal and perform the necessary cleaning.

Is it bad to sit inside a car that smells bad?

Experiencing unpleasant odors inside a car can be just as uncomfortable as being in a hot and sticky vehicle. Regrettably, the occurrence of foul smells from the air conditioner (AC) system is quite common. Numerous factors can contribute to the development of an unpleasant and potentially harmful odor emitted from the car's vents.

There are various reasons for the bad odor that emanates from your car's AC system, as explained by The Family Handyman.

Why does my car air vent smell like rotten egg?

One potential consequence of air passing through a bacteria-filled, moisturized air filter is the emission of an unpleasant odor from the car's AC, causing the air vents to smell like rotten eggs. To avoid these issues and maintain good air quality inside the vehicle, it is crucial to regularly inspect and replace the cabin filter.

Source: Car AC Smells Bad When First Turned ON: Causes & Fixing.