Should You Use Cold or Warm Air Conditioning When Driving in the Rain?
3 Answers
When driving in the rain, it is advisable to use cold air conditioning because the cold air blown onto the windshield forms a thin layer of cold air on the surface, which prevents carbon dioxide from condensing on the glass, effectively defogging it. You can also purchase defogging sprays or anti-fog towels from auto parts stores. Apply the defogging spray to the interior glass surfaces and wipe it clean. This not only removes dirt from the glass but also forms a thin, transparent protective film that prevents moisture from condensing into fog on the glass. The formation of fog on the glass is caused by temperature differences and humidity. When water vapor encounters cold surfaces, it turns into fog. Common defogging methods include: 1. Air Convection Method: Lower the windows on both sides of the car to allow air circulation inside the vehicle, balancing the temperature inside and outside. This method is only suitable for light drizzles, as heavy rain will quickly wet the interior. 2. Cold Air Defogging Method: Using cold air from the air conditioning can quickly lower the interior temperature, making it suitable for emergency defogging while driving. The downside is that it can feel too cold on rainy days, and front-seat passengers may catch a cold if not dressed warmly. 3. Warm Air Defogging Method: Turning on the warm air increases the interior temperature, drying the moisture on the glass to achieve defogging. The drawback is that the fog may initially worsen when the warm air is first turned on, making this method more suitable for use before driving. 4. External Circulation Defogging: Activate the external circulation mode and adjust the air vents to blow air toward the windshield and footwell or just the windshield. While this method is simpler and warmer than using cold air, it is not as fast-acting and may take some time to show results.
When driving in the rain, I find it more suitable to turn on the cold air conditioning because it can quickly dehumidify and prevent the windows from fogging up, ensuring clearer visibility. Fogging is caused by moisture accumulation, and activating the A/C function of the air conditioning can engage the compressor for dehumidification, which is more important than temperature. If it's slightly warm or moderately hot outside, simply turn on the cold air conditioning; but if it's too cold, use the warm air conditioning while ensuring the A/C button is pressed to dehumidify, otherwise, heating alone will make the fog worse. With automatic air conditioning, just press the AUTO button, and it will intelligently adjust the airflow and temperature. For safety, turn it on before fogging occurs to keep the interior dry and avoid accidents. I often do this, especially when driving on highways in the rain, as it quickly dehumidifies and saves effort, eliminating the need to frequently wipe the glass. Also, remember to check if the air filter is clean, otherwise, the dehumidification effect will be compromised, affecting health.
On rainy days, I prefer turning on the cold AC for dehumidification—it's simple and efficient. The cold AC removes window fog better than warm air while freshening the cabin. Fog forms due to external rain and interior breath moisture; cold AC rapidly reduces humidity to prevent blurring. In winter, I use warm air but always engage the A/C button to dehumidify, preventing worsened fogging. Cars with automatic AC are far more convenient—just press AUTO for optimal climate control. With low visibility in rain, early AC activation is key to fog prevention. Though AC consumes some fuel, safety outweighs fuel economy. I've found air recirculation settings helpful too: use inner circulation for faster dehumidification when foggy, then switch to outer circulation post-rain for fresh air. Years of this practice have minimized hassles and extended my AC's lifespan.
