How to Deal with Odor in Car Air Conditioning's External Circulation Mode?
2 Answers
Solutions for odor in car air conditioning's external circulation mode: 1. Short-term odor might come from external air - simply turn off the external circulation; 2. Persistent odor may indicate mold/foreign objects in air intake ducts or a dirty cabin air filter, requiring filter replacement. Drivers should open windows or activate external circulation ventilation shortly after entering the vehicle to introduce fresh air, avoiding keeping windows completely closed. External circulation mode uses fans to draw outside air into the cabin, maintaining constant airflow between exterior and interior. The fan blows outside air, and even when inactive, vehicle movement creates natural airflow into the cabin to replenish fresh air.
I've been driving for over 20 years and encountered smelly AC issues several times when using the fresh air mode. That musty odor is awful, like a damp basement smell. The root cause is a dirty evaporator where bacteria and dust breed in moisture. The solution is straightforward: first, replace the cabin air filter yourself (just buy a ¥10+ one online), then use a dedicated AC cleaner spray through the fresh air intake to dissolve grime before blasting it dry with max fan speed. After using AC, don't turn off the engine immediately—let the fan run for a few more minutes to dry the system. Make it a habit to clean the filter every six months, and odors will significantly reduce. I've tried these methods with instant results—the air inside immediately becomes fresh.
