Smell that? No, we believe that’s not you. But why does your car smell like vinegar, anyway? Well, the reason varies depending on how old your car is and how you use it. For newer cars, the smell is normal and isn’t something you should fret about. It’s a different story, however, if you own an old car that’s emitting a stinging, sour odour.
In case you have noticed, the smell typically originates from the vent of your air-conditioning system. Occasionally, the odour becomes more pronounced when you turn the AC on. In some instances, the smell would go away temporarily—only to return after you have turned off the air-conditioning.
Trapped moisture is one of the primary causes why a vehicle would smell as if someone wants to make a pickle out of your vehicle. Of course, where there’s moisture, microbial infestations would eventually occur, and that’s the culprit behind the sour stench. For that matter, you should be wary of certain areas in your car which could provide the perfect breeding ground for such mouldy or bacterial intrusion. One possible section is in your air-conditioning system.
5 Reasons Why a Car Would Smell like Vinegar
You might find it confusing, let alone worrisome if you are facing this type of dilemma because it’s difficult not to think that someone is trying to put vinegar in your AC vents. Worse, that someone had unintentionally left funky smelling food inside your car.
Though the latter sounds way more plausible than the former, we assure you that neither of which is the cause, considering that you check your car daily. That’s because this nose-pinching dilemma is a common issue among some car owners. That brings us back to our question: what’s causing the fetid, intolerable odour? The reasons why your car could be emitting that vinegary smell is as follows:

1. Dirty Air Ducts
Generally, the accumulation of moisture inside the air-conditioning ducts and vents result in the proliferation of microbes. Thus, what seems like an act of sabotage or negligence is usually attributed to mould infestation.
Typically, moulds thrive in regions that have high humidity levels. When heat and moisture occur inside your car’s air vents and ducts, they simulate the same environment which is conducive to such fungal growth. Once the infestation begins, it’s only a matter of time before you suspect its presence in the form of a vinegary smell.

2. Unclean and Stuffy Air Filter
Among the vital parts of your car’s air-conditioning system, the air filter is probably the most important. Without the air filter, the vents, ducts, and other air-conditioning components will be at the mercy of the dust and other unwanted particles, which could find their way through the cabin, resulting in poor air quality.
If left uncleaned, the filter becomes susceptible to clogging because of the culmination of dust, dirt, and debris. The presence of moisture could also lead to mould infestation, which could worsen the situation. In this case, keeping a well-maintained air filter helps reduce the occurrence of the stuffy, mildewed smell.
3. Too Much Condensation
There are several causes for excessive condensation to occur in your car’s AC system, which if left unchecked could also lead to mould buildup. A malfunctioning drain line is one such cause to look into, while a damaged condensation pan is another.
The reason notwithstanding, the instant you notice that there is a profuse amount of condensation forming along the walls or ceiling of your vehicle, have it checked whenever possible. In this way, you can prevent algae or fungal growth in the ductworks of your car’s air-conditioning.
4. Blocked Condensate Drain Pan
Just as the name suggests, the condensate drain pan collects all the condensation that had formed and dripped from the evaporator core. This component then lets the water flow out of the vehicle through a pipe. However, there can be instances when the condensate pan gets clogged by dirt or dust, which prevents all the moisture out. With all the moisture and microbial growth, it would not take long before your AC vents start to emit that signature vinegary odour.
5. Mildew/Mould in the Evaporator Core
The evaporator core in a car’s HVAC system is highly susceptible to mould or mildew infestation because it provides the perfect environment for fungal growth. With moisture frequently accumulating around the evaporator coil, there’s no shortage of sustenance for the mould or mildew. It would only be a matter of time before you realize what has happened to your air-conditioning system through the intolerable vinegary smell that emanates from the vents.
How to Get Rid of the Stink? — 4 Helpful Tips
When faced with this problem, some car owners are unsure where to begin. Some people would rather choose to take their car to a professional, which is the ideal solution. On the other hand, most people would choose not to shell out a huge sum and perform a DIY instead.
If you choose to fix the issue yourself, the most crucial factor that you should take into account is the drain line. Make sure that it is functioning properly and that all the water dripping from the evaporator flows out as it should be. Apart from that, it helps that you keep the cabin clean and free from any type of liquid spills and the likes.
There is no guarantee that the vinegary smell would disappear forever if you choose to resolve the problem by yourself. Nevertheless, there are surefire ways on how you can minimize or prevent the moulds and other microbes from proliferating inside your AC vents, and they are as follows:
- Using an Automotive Anti-Fungal AC Spray
Some people who have experienced this problem in the past resorted to using household products, such as Lysol and other disinfectants. However, these products can be quite ineffective in resolving the problem. If any, they only minimize the sour odour.
Instead, you may turn to hospital-grade chemicals that have strong, biocidal properties. The other likely items that you may use are antifungal sprays, specifically the ones that are recommended for automotive use. Such products can be bought either online or at auto shops at an affordable cost.
- Preventing Mould Growth
Experts suggest that running the fan for 10 minutes after using the air-conditioning system could help prevent or reduce the likelihood of mould or mildew infestation. In this way, you get to remove all the moisture in the evaporator coil before you finally turn the AC off.
Make sure you are bringing in the fresh air instead of recirculating it. Otherwise, this could only worsen your dilemma. Removing the mould infestation is not something that you can do by yourself. Therefore, enlisting the expertise of a mechanic could be the ideal solution to the problem.
- Cleaning the Air Filters
Keeping the air filters clean on a regular basis does not just help maintain to maintain quality indoor air inside your car cabin, but also prevent mould growth and other related problems. Experts suggest that you should clean or replace the filter every six months. The general rule is that in the event the air smells musky after you turn the AC on, that’s high time that you change the air filter.
- Using a Car Dehumidifier
Car dehumidifiers are an extremely cost-effective way of keeping the cabin bone dry all the time. Not only are these products efficient in absorbing the moisture that accumulates inside the car, but they also help prevent musty odours, which in turn, makes the air breathable. Some car dehumidifier products are in pillow form and can be placed conveniently at the corner of the dashboard or the rear windshield shelf.
Final Takeaway
A vinegary smell in your car is definitive of a mould or mildew infestation. Since this problem originates inside your car’s air-conditioning system, the sour odour would be the least of your problems. Moulds cannot just cause poor air quality inside your car cabin, but also compromise your health. Therefore, addressing this issue in the soonest time possible is your best course of action.
Moreover, there are different ways in which you could handle a microbial infestation as a result of a faulty or clogged air-conditioning component. You can either use products recommended for automotive use, such as an AC anti-mould spray or have the air filter cleaned frequently to avoid going down that road. Regardless of which approach you choose to employ, prevention remains a considerable option, especially in minimizing moisture build-up inside the air-conditioning system.