Foggy car windows are a common occurrence in rainy or humid weather, when there's a temperature difference between the inside and outside of the car, or when the cabin has high humidity. However, simply turning on the air conditioner won't immediately clear the fog. The solution depends on where the condensation is located on the glass surface.
Having bought and used his Hyundai Accent for about 2-3 months, Mr. LNT, residing in Di An ward, Ho Chi Minh City, said: "I've experienced the problem of the windshield and even the side windows near the air conditioning vents fogging up while driving, especially in rainy weather. Even with the air conditioning on, the windows sometimes fog up, making it difficult to see."
In fact, the phenomenon of car windows fogging up even with the air conditioning on is quite common in many car models, especially during heavy rain or rapid temperature changes. This can easily obstruct the driver's visibility and even pose a safety risk if the cause and solution are not understood.
The phenomenon of car windows fogging up even with the air conditioning on is quite common in many car models, especially during heavy rain or rapid temperature changes.
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Why do car windows remain foggy even with the air conditioning on?
According to automotive technicians, foggy windows are primarily related to condensation when the glass surface temperature is lower than the dew point of the air in contact with the glass. When moisture encounters the cold glass surface, tiny water droplets form a white haze, making it difficult for the driver to see.
With foggy windows from the inside, the cause is often high humidity in the cabin air, while the glass surface is cool. Breath from occupants, wet clothing and shoes after rain, damp floor mats, or standing water in the cabin can all increase humidity. In this case, the air conditioning needs to both reduce air humidity and deliver the right airflow to the windows. If only the fan is on without using the dehumidification function of the air conditioning system, the windows may take longer to clear.
Another reason is that the driver hasn't selected the correct air intake mode. When using the recirculating air mode continuously, moisture from passengers and wet items can accumulate in the cabin, especially when the car is carrying many people or driving in prolonged rain.
When using the continuous recirculation mode, moisture from passengers and wet items can accumulate in the cabin, especially when the vehicle is carrying many people or traveling in prolonged rainy conditions.
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Meanwhile, fogging from the outside typically occurs when the glass surface is colder than the humid outside air. This can happen when the air conditioner is running at a high temperature, causing the windshield or windows to be colder, while the outside air is hot and humid.
When encountering foggy car windows even with the air conditioning on, drivers shouldn't automatically assume the fogging is due to a malfunctioning air conditioner. First, it's necessary to identify the location of the condensation on the glass to choose the appropriate solution, avoiding incorrect adjustments that could prolong the fogging.
How to deal with car windows fogging up from the inside.
When the inside of the windshield fogs up, drivers should prioritize using the defroster function first, if the vehicle is equipped with one. Most modern cars have a built-in defroster; drivers simply press the button with the windshield icon (usually with upward arrows) to direct the airflow to the area needing defrosting.
For older car models without an automatic defroster, drivers can adjust the air conditioning to combat condensation from the inside of the windshield. First, keep the air conditioning running, adjusting the temperature to a comfortable level depending on conditions, instead of just using the fan. Adjust the air vents so the airflow blows directly onto the windshield, helping to reduce condensation. Switch to outside air intake when appropriate. If the windshield continues to fog up, slightly increase the temperature and fan speed.
When the inside of the windshield is foggy, the driver should first prioritize using the defroster function if the vehicle is equipped with one.
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If the windows fog up due to excessive moisture in the car cabin, check the floor mats, footwell, and any wet items. Drying the mats, minimizing rainwater entering the car, and regularly cleaning the windows will also help reduce recurrence.
Do not wipe the windshield with your hands or a dirty cloth while driving, as this can distract you, leave smudges, and further impair visibility. If the windshield is so foggy that you cannot see safely, the driver should reduce speed, turn on hazard lights if necessary, and find a safe place to stop and address the issue.
The glass is frosted on the outside, what should I do?
If condensation forms on the outside of the windshield, causing it to fog up from the outside, the driver can use the wipers to clear it if the windshield is equipped with wipers and the surface is sufficiently wet. For the side windows, the appropriate wiper or wiper function can be used if the vehicle has one. If the windows continue to fog up, reduce the cooling level or slightly increase the air conditioning temperature to prevent the glass surface from becoming too cold compared to the outside air. Adjust the airflow direction to avoid blowing cold air directly onto the area of condensation.
However, it's important to note that increasing the temperature isn't always effective in addressing fogging caused by outside the window. Depending on weather conditions and the air conditioning system's design, drivers should try adjusting the temperature gradually while observing the glass's reaction.
If condensation is detected on the outside of the windshield, causing it to fog up from the outside, the driver can use the windshield wipers to clear it if the windshield is equipped with wipers and the surface is sufficiently wet.
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For windshields, if condensation only appears for a short time, using the wipers is usually a quick fix. Avoid turning on the defroster or increasing the temperature excessively without identifying the exact location of the condensation, as this may not address the root cause.
Additionally, dirty, oily, or improperly coated windshields can cause water to streak, reducing visibility in the rain. Drivers should clean their windshields with a specialized solution, check the condition of the wiper blades, and replace them if they are not cleaning effectively.
When driving in heavy rain, if visibility remains limited even with the air conditioning and wipers on, drivers should not attempt to continue at high speeds. Reduce speed, maintain a safe distance from the vehicle in front, and stop at a suitable location if visibility is impaired.
For windshields, if the condensation on the outside only lasts for a short time, using the wipers is usually the quickest solution.
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It's crucial to determine whether the fogging is from the inside or outside before addressing it. Properly adjusting the air conditioning, airflow direction, air intake mode, and wiper system will help clear the car's windows quickly, maintain visibility, and reduce the risk of accidents when driving in adverse weather conditions.