Why Does Car Glass Fog Up After Turning on the Air Conditioning?

[McEdward]

Car glass fogs up after turning on the air conditioning due to the significant temperature difference between the interior and exterior environments, causing the glass temperature to drop too low. This leads to the condensation of high-humidity outside air on the glass surface. The key to defogging the glass lies in reducing the temperature difference and humidity on both sides of the glass. Measures to defog car windows include using the defogging function buttons for the front and rear windshields. Pressing the corresponding switch will activate the defogging function. Alternatively, when first entering the car, turn on the warm air and direct it toward the windows. Since warm air rises quickly, it provides effective heating. Then, switch to the external air circulation mode to minimize the temperature difference between the inner and outer layers of the glass, which can quickly remove fog. Another option is to purchase specialized anti-fog agents or windshield defoggers designed for car windows. These products automatically absorb moisture on the glass, forming a water film that prevents fogging. You can also slightly open the windows to balance the temperature; avoid directing the air conditioning toward the windows. Applying dish soap or soap to the car windows can also create an anti-fog effect, as these detergents disrupt the attraction between water molecules, reducing surface tension.