How to Deal with Fogging on the Outside of the Car Windshield?
4 Answers
Solutions for fogging on the outside of the car windshield: When the fog is not heavy, you can appropriately open both side windows to allow air convection, which eliminates the temperature difference on both sides of the windshield, making it difficult for fog to form. Alternatively, turning on the air conditioner's cold air can quickly remove the fog. The principle of defogging agents is simple; spraying a layer on the windshield forms an effective protective film that prevents water vapor condensation. However, this protective film has a short lifespan and requires frequent reapplication to maintain its effect. If the system detects impending fogging, the air conditioning system initiates a series of defogging operations, such as adjusting temperature, airflow direction, air volume, and internal/external circulation. Blowing cold air provides a quick but temporary solution, while blowing hot air can fundamentally solve the problem of windshield fogging.
I just encountered this situation last week when it was drizzling, and the windshield suddenly became foggy with the AC on. Immediately, I turned up the AC temperature by two degrees, adjusted the vents downward to avoid blowing directly on the glass, and turned the wipers to the first speed. Remember not to use cold air on the glass—the greater the temperature difference, the heavier the fog outside. If the humidity inside the car is too high, crack the window slightly or turn on the external circulation for a few minutes. In a hurry, you can wipe the outside of the glass with a towel dipped in alcohol, which can last for about half an hour. Every time you wash the car, remember to use glass coating agent—rainwater will hardly cling to the glass.
Veteran driver shares a tip: Avoid setting the AC to the lowest temperature; keeping it around 24°C is most effective in preventing fogging. Adjust the central vents to blow air toward the feet and angle the side vents toward the rearview mirrors. If the windshield fogs up, gently use the wipers. Remember, oil film on the outside of the glass can worsen fogging—buy a glass cleaner from the supermarket and wipe it twice a month. In winter, carry a chamois cloth and wipe the windows at red lights for a cleaner result than using wipers. Don’t forget to turn on the rearview mirror heating function to keep both mirrors fog-free for safety.
Fogging is primarily a physical phenomenon caused by the direct blowing of cold air from the air conditioning onto the windshield. Immediately turn off the front defogging mode, reduce the fan speed by one level, and adjust the temperature to above 22 degrees Celsius. Simultaneously activate the rearview mirror heating function to avoid complete loss of visibility. If fogging persists, it indicates excessive humidity inside the vehicle; turn on the external circulation for five minutes before switching back to internal circulation. Spraying windshield washer fluid can provide an emergency solution, but addressing the temperature difference between the inside and outside of the window is the fundamental fix. After parking, wiping the outside of the windshield with a mixture of dish soap and water can delay fogging.
