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Hey, Why Does My Car AC Smell Like Vinegar?

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Four common causes for a vehicle overheating after turning the A/C on and their related parts.
When your vehicle starts to smell like vinegar or has a foul smell is an indicator that the conditions are perfect for mold and mildew to begin to grow. There are various places where this can happen. The most common is in the evaporator core due to the condensation from water vapor collected on the evaporator during the cooling process. When the air conditioner has shut down, the ambient air temperature is warm enough to create the perfect environment for the mold and mildew to start growing in the evaporator and AC vents.

Does Your Car Smell Like Vinegar After You Turn The AC On?

The vinegar smell is probably due to moldy substances built up in the air conditioning system. This could be caused by a clogged air filter, moldy evaporator, or even something rotten inside the system. Alternatively, a food substance spilling in the vehicle or a sunroof leak could be culprits. More rarely, the smell could come from sulfated batteries releasing fumes; this is particularly noticeable when the AC is not in recirculation mode.

Ensuring your vehicle's AC is blowing fresh air is essential for comfort. Remember, a small problem ignored today can become costly and dangerous tomorrow. So act now, and stay safe on the road!

Let's Get To The Bottom Of It!

  • Q: Are the vehicle's carpets becoming wet after going through the rain or a car wash?

    The sunroof and doors have a unique rubber to keep water from dripping into the car. It also has a tube that removes water if it gets around its edges. The tube passes through a part of the car called the A-pillar before getting to the ground. But if the tube gets blocked, broken, or comes off, water can leak inside the vehicle. This can make the roof inside the car look worn or make the carpet wet on the driver's side near the bottom part of the door after it rains or after the vehicle is washed. Hence, if the carpet is unclean, a vinegar smell can develop.

  • Q: Does the vinegar smell also has a musty scent?

    The evaporator core in your car air conditioner makes the air cold by removing water particles. Sometimes, the core gets so cold that it freezes the water and turns it into ice. Later, the ice melts and turns into water again. But, when it's warm outside, and water is left in the core, it can grow mold and mildew. When this happens, the air from your air conditioner might smell like vinegar.

  • Q: Is the shifter somewhat greasy and sticky?

    The cup holders in your car are near the gear shifter, so if you spill your drink, it can go into the shifter and get the carpet under the center console wet. This creates a damp place for mold and mildew to grow. In addition, the substance can dry and make the gear shifter stick and get stuck, almost like it's glued there. This can cause damage that might require replacing the whole gear shifter assembly.

  • Q: Apart from the vinegar smell, do you also notice a rotten meat scent?

    The air vents and ducts inside your car can be an excellent place for rodents to hide and stay warm. However, when a rodent gets deep inside the air conditioning system, it might get stuck without escape and eventually die. Turning on the air conditioning or heat makes the airflow pass through the poor critter's corpse. Consequently, the car AC smells like vinegar and rotten meat.

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Vehicle Health Inspection Proof

Explore the following typical inspection results that show a potential cause for the symptom and select the one you believe is similar to your vehicle's issue.

Leaking sunroof

The proof image shows the disconnected sunroof drain tube causing the water to leak onto the driver's carpet.

A customer brought in their car because they noticed the carpet on the driver's side was getting wet every time they went through the car wash. They thought the windshield or the driver's door seal was leaking, but they couldn't find any visible leaks.

The technician took the car for a test drive and noticed nothing wrong. During the vehicle health inspection, they saw nothing about the customer's concern. The technician needed to perform an authorized further investigation.

To figure out where the water was coming from, the technician used a smoke machine and had an assistant sit in the car and look for smoke coming through any leaks. They still couldn't find any leaks, so the technician checked around the sunroof to see any signs of leaks there but found nothing.

Finally, the technician started pulling back the carpet around the driver's side and found that the sunroof drain tube was removed from the rubber grommet that goes through the kick panel. This was the leak source. The technician reattached the drain tube and secured it with weather strip adhesive.

To fix the problem, the technician recommended that the customer leave the windows down for a few days to dry the carpet inside the car.

Does the issue look like this? if not accessible your shop will document it
Sticky shifter

The proof image shows residue from the spilled liquid, identified as soda.

When the customer dropped off their car, they said they had trouble getting the shifter out of the park; it was too sticky. During a test drive, the technician confirmed that the shifter was sticky and saw some residue.

However, during a vehicle health inspection, the technician saw nothing related to the customer's initial concern.

To further investigate, the technician took apart the center console bezel and found that a large amount of sticky liquid had been spilled on the shifter. This caused the park switch in the shifter assembly to become gummed up and rusted.

Unfortunately, because the liquid got into the electrical components of the shifter assembly and affected the switches, the whole shifter assembly will need to be replaced.

In addition, the technician recommends detailing the car's interior because the carpet on either side of the center console is sticky and damp with fluid.

Does the issue look like this? if not accessible your shop will document it
Faulty a/c drain

The proof image shows that the wet carpet was due to the air box drain being disconnected, which caused the water from the air conditioner to leak onto the passenger's carpet. This can develop into more problems for the AC unit.

A customer dropped off their car at the repair shop because they noticed the carpet on the passenger side was regularly wet. They thought there was a problem with the heater core.

During the vehicle health inspection, the technician found the carpet underneath the glove box damp but didn't notice anything more related to the customer's concern.

The technician raised the car on the hoist to check the evaporator drain tube, which drains the water that forms on the car's air conditioner evaporator. They used a wire to check for debris in the drain tube but found nothing.

Then, they lowered the vehicle and pulled back the carpet to access the drain tube from above. They found it had come loose from the air box and tried to reattach it, but the tube clip was broken. This means the evaporator drain tube needs to be replaced.

To prevent mold and mildew from growing in the carpet, the technician recommended that the customer leave the windows down for a couple of days outside to dry the carpet. This is important because if the carpet stays wet, it can start to smell and cause health problems.

Does the issue look like this? if not accessible your shop will document it
Clogged cabin air filter

In the photo provided as proof, you can see the clogged cabin filter with wet leaves, the culprit behind the poor airflow and musty smell.

A customer brought in their vehicle complaining that the air from the vents was weak and had a strange, musty smell.

During a test drive, the technician confirmed that the air from the vents was weak and that a strange vinegar smell came from it.

Upon conducting a vehicle health inspection, the technician found wet leaves in the cabin air filter, almost completely blocking it. This blockage was restricting airflow and causing the foul smell the customer noticed.

The technician recommends replacing cabin air filters when they get to that condition and performing an evaporator cleaning service to remedy the issue. This will help prevent mold or mildew from growing on the evaporator core and causing further issues.

Does the issue look like this? if not accessible your shop will document it
Dead critter

As evidence of the cause, an image shows the dead mouse lodged in the blower motor fan, which is responsible for the unpleasant odor in the vehicle.

When the customer brought their vehicle in, they mentioned it had a foul smell, as if something had died inside. They also noticed the blower motor was louder than usual, and the airflow didn't feel as strong as before.

During a test drive, the technician confirmed that the blower motor was making an unusual noise and that a strong odor resembled a dead animal inside the vehicle.

While conducting a general inspection of the vehicle's condition, the technician noticed that the cabin air filter had been damaged by rodents and needed to be replaced. Since this required additional diagnostic work, the shop got customer authorization.

To investigate further, the technician began by removing the blower motor assembly. Inside, they discovered a dead mouse in the squirrel cage of the blower motor.

The technician recommends removing and cleaning the squirrel cage using a disinfectant to address this issue. They also suggest blowing out the air ducts and car vents with compressed air to remove any remaining debris.

Disinfection and deodorization should also be performed on the intake air box and evaporator to eliminate any traces of rodent excrement and the accompanying smell.

Does the issue look like this? if not accessible your shop will document it
Moldy evaporator

The provided proof image shows the evaporator core covered in mold and mildew, responsible for the vinegar odor when the AC is turned on.

When the customer dropped off their vehicle, they mentioned a foul odor from the AC vents during the monsoon season. They were concerned that there might be a freon leak in the car since they smelled vinegar. However, they confirmed that the AC was working fine.

During the test drive, the technician noticed the AC vents' pungent, musty, moldy odor. However, the technician found nothing more related to the customer's concern during the vehicle health inspection.

Later, the technician removed the cabin air filter and inspected the evaporator core. The technician found mold growing on the evaporator core, which could explain the foul odor. Thus, the technician recommends an evaporator disinfecting deodorizing service to clean out the evaporator core.

In conclusion, the customer didn't keep the evaporator's cleaning up-to-date, resulting in a mold buildup. Thus, the technician suggests an evaporator disinfecting deodorizing service to eliminate the mold causing the odor.

Does the issue look like this? if not accessible your shop will document it

Typical Fixes to Address the Cause(s)

The following chapters bases themselves on experiences from our auto repair shop; we'll describe related problems' causes and fixes.

"Cabin air filter replacement" fixes "Clogged cabin air filter"

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Hey, Why Does My Car AC Smell Like Vinegar?
Sometimes a problem is more challenging to describe than it initially looked like. If you are not sure your problem is described by this article, please find below similar vehicle symptoms, which might describe better the issue you are experiencing.

Other things your auto repair shop might talk about:

Cold air. air intake. ac system. all the windows. fresh air intake. warm air.