What Causes Persistent Fogging on the Outside of the Windshield?
2 Answers
The reason why the outside of the windshield cannot be defogged may be due to moisture on the exterior after rain. Here are the relevant explanations: 1. Temperature difference between inside and outside the car: Primarily, the large temperature difference between the interior and exterior causes cold air to hit the glass, leading to external moisture condensing on the surface. This is a basic principle of physics. A significant temperature difference between the cabin and the outside or rainy conditions can cause fogging on the windshield and door glass, posing a safety hazard for driving. 2. Precautions: Regularly clean debris and snow near the air conditioning intake to ensure the system functions properly. Generally, the ventilation mode should be set to external circulation to promote better airflow.
I often drive, especially on damp mornings or rainy days, and it really annoys me when the fog on the outside of the windshield won't go away. The main reason is the temperature difference: the heater inside the car is turned up high, while the outside air is chilly, causing the warm air to condense into fog on the glass when it meets the cold. Additionally, high humidity doesn't help—like on rainy days, the fog becomes more stubborn. When the wipers swipe it away, it comes right back, possibly because the wiper blades are old, not cleaning properly, or deformed. Also, if the air conditioning is set incorrectly, such as having the airflow directed straight at the windshield, the cold air can actually make the fog more noticeable instead of eliminating it. I've tried solutions like adjusting the car's air conditioning to blow toward the feet or the front, avoiding direct airflow onto the windshield, and turning on a bit of external circulation to let the air flow. When temporarily parked, slightly opening the windows can reduce the temperature difference between inside and outside, making the fog easier to disperse. If the wipers aren't working well, simply replacing them with new ones is an easy fix. However, this situation seriously affects driving visibility, especially at night, and can easily lead to accidents, so never force yourself to drive under these conditions—find a safe place to address the issue before hitting the road. I think regular vehicle maintenance, replacing wipers, or cleaning the air conditioning vents can help prevent this problem.
