What Causes Odor When Using the Car's External Air Circulation?
4 Answers
The reasons for odor when using the car's external air circulation include mold or foreign objects in the air intake ducts or a dirty car air filter. Below is an introduction to issues related to the car's external air circulation: 1. Mold or foreign objects in the air intake ducts: The car's air conditioning ducts can easily accumulate dust, which over time can produce odors, necessitating cleaning of the car's air conditioning system. 2. Car air filter: The car air filter is the most easily overlooked component. It requires regular cleaning and replacement. However, a dirty car air filter not only fails to filter out dirty air but also causes secondary pollution to the fresh air entering the car. Therefore, to completely eliminate odors inside the car, it is essential to address the source of the problem.
When there's a foul odor with the car's external air circulation on, it usually stems from accumulated dirt in the AC system. Through years of driving, I've found the root cause is often a dirty cabin air filter—it constantly filters outside air, eventually clogging with dust, pollen, and bacteria. Combined with moisture in the ducts, mold spots thrive during rainy summers, resulting in smelly airflow. Severe external air pollution, like exhaust or garbage odors, may also enter. Another overlooked culprit is dust buildup on the evaporator surface, which becomes a stench source if not cleaned promptly. The solution is straightforward: replace the filter regularly (biannually is ideal), occasionally spray antibacterial cleaner into the AC system, and switch to recirculation mode to blow dry air for a few minutes before parking to prevent moisture retention. These steps significantly reduce odors, ensuring fresher air throughout your drive.
A strange smell when the car's external air circulation is on is mostly due to issues with the air conditioning system. The air filter is the most common problem area. If it hasn't been replaced for years, dust and pollutants can accumulate there, releasing unpleasant odors when air blows through. The air ducts and evaporator surfaces are also prone to mold, especially in high-humidity environments where mold grows faster. Sometimes, external air carries industrial pollutants or roadside garbage smells, which get directly sucked into the car, making it naturally unpleasant. As someone who enjoys tinkering with cars, I recommend first using a multimeter to check the air conditioning switch status and ensure the external circulation pathway is clear. Then, replace the air filter yourself—it's super cheap to buy parts online. For cleaning the air ducts, use a professional spray and follow the instructions for one or two rounds. Don’t forget to turn off the air conditioning before parking each time to keep it dry and prevent mold.
Odd smells when using the external air circulation often stem from minor issues. A dirty cabin air filter starts to stink as it accumulates too much dust, mixing external odors into unpleasant smells. Uncleaned air ducts develop mold spots, breeding bacteria that release strange odors with the airflow. I frequently encounter this during my daily commute, especially in congested areas where outside exhaust fumes rush in, making the car interior smell bad. To solve this, I make it a habit to inspect and replace the filter every few months—a small cost for great peace of mind. I also use disinfectant sprays to clean the air ducts, just a simple spray from a kit. Pay extra attention during rainy or hot weather to keep the AC system dry.
