Why Does Car AC Smell Like Vinegar? [ Get Rid of Molds and Burnt Plastic Smell]

A common problem that many car owners face is that their car’s air conditioning system smells like vinegar. In this post, we will explain the reason behind this unpleasant odor and show you how to get rid of it.

So, why does car AC smell like vinegar? Car AC smells like vinegar due to the growth of bacteria, molds, and fungi in AC vent tubes. The air conditioner vents can get really smelly due to the growth of fungus, mold, and bacteria. Also, as a result of water condensation on the evaporator coil, mildews grow on the coil which causes a pungent acidic smell in the car. Also, car AC vents may contain an accumulation of some organic substances like leaves that undergo a fermentation process as they decay and produce alcohol which in turn causes an acidic vinegar-like smell. Another reason for the acidic vinegar smell in a car is the dirty cabin air filter. The air filter gets clogged with debris, pollutants, moisture, and dust over time. The dirty air filter causes pollutants to enter the cabin area of the car along with an unpleasant vinegar-like odor. Lastly, the leakage of car AC refrigerant can also cause an acidic and vinegar-like smell in the car.

The best way to remove a vinegar smell from a car air conditioning system is to buy an HVAC antifungal spray. This spray will help prevent the growth of fungus and will eliminate any bad smells in the car.

If it doesn’t resolve the issue, you can take your car to your mechanic.

Here are the possible reasons for a vinegar smell coming out of the car ac.

  • Dust and debris in the car cabin air filter
  • Dirty car intake and AC vents
  • Leaking refrigerant of the car AC
  • Moldy evaporator coil and fins
  • Clogged catch basin of condensate
  • Build up of organic material in car AC
  • Damaged components of car AC
  • Faulty Blower Motor
  • Ozone emission from electric air conditioner motor 
  • Fuel fuel filter
  • Faulty fuel pressure sensor
  • Leaking chemical out of car battery

1. Dust and Debris in Car Cabin Air Filter

The cabin air filter is the most important component of your car. It is a part of the ventilation system of your vehicle. It is responsible for removing dust, pollen, debris and other pollutants from the air that passes through it.

Your car’s ventilation system will remove some of this harmful pollution, but the filter should be replaced after the car has 15000 to 30000 miles. 

If you notice a musty odor coming from your vehicle, it could be a sign that the cabin air filter needs to be replaced. You should not hesitate to contact your mechanic if you notice a strong smell of vinegar. I would recommend using K&N Cabin Air Filter as it smells like a fresh clean rubber.

Check out the below video to learn how to replace the cabin air filter.

2. Dirty Car Intake and AC Vents

If changing the air filter does not eliminate the vinegar smell from AC in a car, there are chances that car intake vents are dirty. Both the intake and AC vents of a car can be clogged with dust and mildews due to humidity and moisture traps. If vents are dirty, they tend to trap the fumes, which in turn can give rise to unpleasant odors.

Follow these steps to clean the car vents so that you can get rid of the vinegar-like smell in a car:

  • Turn the interior (cabin) fan on to a maximum speed
  • Roll down the window of car doors so that air can be exchanged
  • Make sure to turn off the recirculate button so that the car interior can be replenished with the fresh outside air
  • Take Lysol spray and spray it into the vents in front of the windshield. Lysol spray will kill 99% of bacteria and molds in the car vents. Moreover, the Lysol spray will also remove any organic material stuck clogged in the vents.

In this way, your car vents will be cleaned out of any kind of dust, organic material, and molds.

You can check out the below video to learn more about cleaning car vents.

3. Moldy Evaporator Coil and Fins 

The molds that are grown on the evaporator coils and fins of the car air conditioning system due to the puddle of moisture also cause a vinegar smell from car AC. This is because the water vapor in the air gets cooled down and condensed on the evaporator coil. Also, the A/C evaporator drain may be blocked and the buildup of water is causing the musty smell.

To prevent the buildup of moisture on the evaporator, I will recommend that you should turn the car A/C off a minute or two before you get home or park your car and leave the fan running to the max to dry the system out so that there is no condensation buildup on the car air conditioning system.

To clean the evaporator of car AC, you can use this Lubeguard Kool-IT Evaporator foam cleaner. All you need to do is to locate the condensate drain tube and inject the plastic extension of the foam cleaner into it. Resultantly, the cleaner will foam up and coat the entire evaporator coil. It will kill the mold and wash it down the drain, leaving a protective layer.

You can check out the video below to understand the procedure of removing the molds off the evaporator coils of a car air conditioner.

4. Clogged Catch Basin of Condensate

If the condensate catch basin is blocked with debris, the condensate will start leaking into the car cabin and cause a vinegar smell from the car AC.

Condensation is the water vapor that is produced from heat and cold. When the air conditioner is running, it is producing moisture. The condensate drains to the outside of the unit and flows to the ground via a drain line. This can become clogged with debris, dirt, and mold.

You should inspect the drain line from the unit, as well as the surrounding area. If you find that there is a buildup of debris, you may need to clean out the drain line. If you do find that mold or algae is growing in the drain line, you will need to remove it. If the drain line is clogged, water will accumulate in the catch basin which will stimulate algae and mold growth. Eventually, this will cause a vinegar smell in a car.

To kill molds and clean the drain tube of the car condensate system, you can use Lubeguard Foam Cleaner I mentioned above.

5. Coolant or Refrigerant is Leaking

Refrigerant leakage in the cooling system of a car can also be the cause of a vinegar smell in a car. Refrigerant is a liquid chemical compound that is used in air conditioning. Refrigerant leakages can occur in many ways. The most common reasons include damage to the compressor, loss of seal, faulty connections, faulty repair work, and poor maintenance. The odor of leaking refrigerant is a result of the breakdown of the refrigerant itself and it will gradually get stronger with time. 

Moreover, the acidic chemical in the car can also be caused by the antifreeze or coolant leaking into the cooling system. If you are sensing a sweet smell like baked bread in a car, there are chances that the coolant (antifreeze) is leaking out of the heat core. To verify this, keep watching the antifreeze level of your car to see if it is going down. Furthermore, turn on the defrosters and see if they blow any greasy mist onto the windshield. If your coolant level drops or you notice a greasy film on your windshield, take your car to the dealership and get the heater core tested for a leak.

Chemical is Leaking Out of Car Battery

Lead acid or nickel metal hydride batteries can emit hydrogen sulfide when they fail. Hydrogen sulfide smells like a rotten egg which causes a pungent acidic smell in a car. The hydrogen sulfide gas is produced by the car battery when the electrolyte (chemical in the battery) level is quite low.

The vehicle’s battery may start to leak acid as it ages. This can happen because of corrosion in the terminals. Also, overcharging will cause the car battery body to expand and leakage of electrolyte. If you are experiencing these symptoms, you need to take your vehicle to your dealership as soon as possible. 

6. Faulty Blower Motor of Car AC

The blower motor is an electric device that pushes heated or cooled air into the car cabin. The blower of a car AC is a motor and fan assembly fitted with electrical connections. If there is a burning plastic smell in a car, the chances are that the car AC blower motor is malfunctioning. This usually happens when the electric connections of a blower are clogged with dust and debris. 

7. Clogged Fuel Filter

The exhaust system of a car is designed to remove unwanted emissions from the engine. The catalytic converter converts harmful gases into harmless ones before they are released into the atmosphere. When the fuel filter fails to remove impurities from the fuel, the fuel combustion can produce gases such as hydrogen suphide, that have a strong pungent smell. As a result, a clogged fuel filter could be the cause of the acidic vinegar smell in a car.

8. Faulty Fuel Pressure Sensor

If the fuel filter is clean, your car can still experience bad odor emissions due to a faulty fuel pressure sensor. If the fuel pressure sensor goes bad, it will result in an insufficient fuel supply to the combustion chamber. As a result, inefficient fuel combustion will take place which will make the catalytic converter unable to process all exhaust byproducts that exit car via the tailpipe.

How To Remove Vinegar-like Smell From The Car?

Follow these steps to remove the vinegar smell in a car.

  1. Make sure that the carpet on the passenger side floor of a car is not wet.
  2. If the cabin air filter is dirty, replace it.
  3. Turn off AC 5 minutes before parking your car and set the fan to the maximum while keeping the recirculation button off.
  4. Use shampoo to clean your car seats and mats regularly. It also improves the smell in the car.
  5. Try baking soda solution. Sprinkle it in the car. Let it settle for a few hours and vacuum it later. It helps neutralize the smell of vinegar in a car
  6. Check for things between the car seats and the center console. This gap between the car seats is where lost items go and rarely come out.
  7. Have preventive maintenance of important parts of a car such as fuel filter, pressure sensor, car battery, and AC blower motor.
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