Will Water Enter the Car When Using the External Circulation in the Rain?
3 Answers
Using the external circulation in the rain can allow water to enter the car. Introduction to External Circulation: External circulation refers to activating the ventilation mode of the air conditioning system, ensuring fresh air enters the car. However, during rainy weather, rainwater may also enter the car along with the air while driving. How to Use External Circulation: When using the internal circulation for an extended period and it is inconvenient to open the windows, periodically switch to external circulation to allow fresh air into the car. If there are many passengers in the car, using external circulation helps maintain air freshness and prevents excessive humidity inside, which could lead to window fogging. Defogging Function: To address this issue, cars are equipped with a windshield defogging function, controlled by a button on the air conditioning panel.
When I first bought my car, I was always worried that turning on the fresh air mode in the rain would let water in, thinking rainwater might flood through the vents. But in reality, car design is quite thoughtful—the fresh air intake is hidden above the engine compartment, protected by grilles and drainage holes that keep water out. In light rain, not a single drop gets through, and it still brings in fresh air to keep the cabin comfortable. However, I remember during last year’s heavy rain season in the south, when the windshield wipers couldn’t even keep up, I tried using fresh air mode and felt some moisture fogging up the vents. Later, I realized it’s safer to switch to recirculation mode during heavy downpours. Turning on the defogger with the AC instantly cleared up visibility. Now, I make it a habit to check the cabin air filter during regular maintenance to prevent clogging. Once you develop this habit, rainy days won’t be a problem anymore, and the car runs smoother too.
From the perspective of automotive air conditioning construction, when the external circulation mode draws in outside air, it passes through the filter element at the intake and the drainage system. Normal rainwater is filtered out, with almost no water entering the cabin, as the design already considers rain protection. However, during extremely heavy rainfall, such as during a typhoon, high wind speeds may carry some water mist inside, which isn’t actual water ingress but can affect comfort. In such cases, switching to internal circulation or using the dehumidification mode is more practical. For daily maintenance, pay attention to the condition of the air filter—replace it if it’s aged to avoid water accumulation risks. After all, as a car ages, minor issues may arise, so don’t overlook these details to ensure a worry-free and smooth driving experience.
