How to Get Rid of Fog on Windshield
There are multiple ways to deal with condensation and fog on your windshields, given the temperature and environmental conditions. Generally speaking, we're talking about fog on the interior of the glass.
The reason for this is because cold outside air is less humid than the warm air inside your vehicle, combined with body heat and moisture from breath. This contrast in heat and humidity is what causes your windshield to get fogged up.
What's the Fastest Way to Defog a Windshield?
As you might imagine, cooling the interior air of your vehicle is a quick way to balance the temperature on the outside of the glass. This will prevent additional fog and begin to clear your windshield.
One way to do this is to simply open a side window. You can also activate the defrost vent and turn the heat off in your vehicle until your visibility returns. Using an appropriate windshield washing fluid that won't freeze or clog up your vehicle's systems is also important.
The reduction in moisture and lower temperature is fast acting. However, this clearly isn't the ideal way to reduce or eliminate interior fog, as it's significantly less comfortable to drive this way in colder climates.
How to Defog Your Windshield in Comfort
While less fast acting, keeping your car warm is effective with the right defrost settings. For example, rather than trying to match outdoor temperatures and conditions, you can use your heater to warm up the exterior of the glass.
You can deal with the moisture inside your vehicle by using the defrost vent feature. This will move warm air across your windshield, causing the condensation to evaporate. However, do not use the air re-circulation setting if your vehicle has one, as this will keep moisture inside and prevent dry air from entering. As you know, this can make the situation worse, rather than better.
How to Defrost Your Windshield in Hot and Humid Climates
The same issue of imbalance in heat and moisture between the interior and exterior applies. As you might know, extreme changes in temperature are one of the main reasons why windshields crack, in addition to fogging up.
In this case, it's too humid on the outside of your windshield and too dry inside your vehicle. The condensation turns into moisture on the glass, almost as if your vehicle is constantly sweating.
Using your windshield wipers isn't exactly ideal, although you are dealing with exterior condensation. It can cover your windshield with streaks, not to mention the repeated back and forth process.
Again, you can match the temperature and humidity levels by turning off your air conditioning. You could also go so far as to warm your vehicle up a little to strike that perfect balance. In addition, a windshield replacement might be required if the glass just isn't capable of keeping heat and humidity consistent.
How to Prevent Fogging
Believe it or not, a cleaner windshield is much less prone to developing fog in either type of climate. You can remove hard water spots and generally keep the glass free from debris and other elements to reduce your exposure to fog.
Another method is to use an anti-fog windshield treatment. These are sometimes applied by the manufacturer, although you can certainly do this yourself at home. Solutions like Aquapel and Rain-X can be used to prevent interior fog, and are especially valuable in colder climates. Depending on the type of auto glass you use, it might be more durable or capable of handling harsher climates as well.
How to Get Rid of Fog on Windshield
Source: https://www.dealerautoglassaz.net/auto-glass-phoenix-blog/how-to-defog-windshield/