Why does the car air conditioner have a sour smell?

[LeviMarie]

Reasons for the sour smell in car air conditioners: When the car air conditioner is cooling, it lowers the temperature of the air through the evaporator unit. During operation, the temperature of the evaporator can drop to around 0 degrees Celsius, making it function similarly to a refrigerator. The cooled air then enters the cabin. The damp environment inside the evaporator provides an ideal condition for fungal growth, which is the source of the sour smell. The car air conditioning system is designed to cool, heat, ventilate, and purify the air inside the vehicle, providing a comfortable environment for passengers, reducing driver fatigue, and enhancing driving safety. As such, the air conditioning system has become one of the indicators for evaluating whether a car is fully equipped.

[StLincoln]

The sour and foul smell from the car air conditioner is mainly due to accumulated water on the small metal evaporator that hasn't dried thoroughly, leading to mold and bacteria growth over time. This issue is particularly common in hot and humid summers because frequent AC use generates more condensation. I recommend first checking the cabin air filter to see if it's too dirty or clogged with dust—replace it immediately if needed. For DIY cleaning, you can purchase a specialized AC cleaning spray, apply it through the air intake, and let the fan run for a while to blow out residues. However, be cautious to avoid damaging electrical components. If the odor persists, the evaporator might be clogged internally, requiring professional cleaning at a service shop. Ignoring this issue not only affects driving comfort but may also trigger coughing or allergies. Moreover, prolonged neglect can lead to higher power consumption.

[DelGrace]

The air conditioner emits a sour smell, reminding me of the same issue I encountered last summer when taking my kid out. Worried it might affect my child's breathing, I looked it up and found out it was due to mold growth from accumulated water in the AC's internal evaporator. Those molds thrive in damp areas, and once the air circulates, the odor spreads. I learned to handle it at home: first, turn off the AC and let the fan run for a few minutes to dry the system, then spray a cleaning solution made of white vinegar and water. Luckily, I dealt with it promptly without spending much. Now, before parking, I make it a habit to turn off the cooling and let the system dry thoroughly to avoid moisture buildup and potential health issues. My kid feels much more comfortable in the car now. Don’t underestimate that smell—it might attract pests or rodents into the ventilation ducts.

[DelTanner]

Air conditioner smells sour? I've encountered this too. Last month, I bought a used car and noticed a strange smell as soon as I turned on the AC. After checking online, it was said that the evaporator had mold. It's mostly because water droplets didn't drain properly during cooling, leading to bacterial growth and a sour, musty odor. I simply bought a can of automotive cleaner, sprayed it into the AC's external circulation vent, turned on the fan at high speed for 10 minutes, and the smell was gone. It's advisable to regularly check if the filter needs replacing, otherwise, more dust accumulation will worsen the smell. Checking before long trips is also a safer bet.