Defog Windshield: How to Remove Fog from Car's Windshield?

The fact that you are reading this means you have encountered a foggy windshield at some point. It could be an occasional occurrence, or a bane that troubles you every single time you get into your car to drive. It can come across as a rather simple problem, which many people just choose to live with, but it has the potential to manifest into an even bigger problem.

If your vision is obstructed due to a fogged up windshield, the hampered vision of the road can make it dangerous to drive, or can lead to  an accident in the worst-case scenario. Knowing this can be troubling, and an easy solution is to simply keep a clear windshield.

What causes a foggy windshield?

A windshield can fog up either from the inside, or from the outside, and you will need to employ different strategies in both scenarios.

If your windshield is fogging up from the inside, it is because of excess moisture inside your car’s cabin. On cold mornings, the windshield temperature drops while the temperature inside the cabin stays relatively warmer as it is an enclosed space. As the temperature difference increases, more and more moisture condenses on the glass area of the car. This leads to a foggy windshield on the inside. This type of fogging on the windshield usually happens in the winter.

If your windshield is fogging up from the outside, it is because your windshield temperature is lower than the ambient temperature outside, and the outside air is also highly humid. In this case, the windshield temperature is lowered by the excess use of air conditioning inside the cabin, which over time cools down the windshield of your car. As you keep driving and the windshield becomes colder and colder, the outside air starts depositing more and more water vapour on the glass. This leads to a foggy windshield on the outside and this type of fogging happens predominantly during the monsoon.

How to remove fog from your windshield?

Now that we know that fogging can occur on either side of the windshield, and in different conditions, let us get down to tackling the problem. What you must know are the short-term methods for windshield defogging, and the long-term methods for windshield defogging. These can be contradictory to each other, and therefore, one must use a mix of both techniques to achieve the desired results.

Tips to defog the windshield from the inside

We have already discussed that the inside of a windshield fogs up in the winter, especially in the morning. You will encounter this problem the first time you take your car out in the morning. In such a scenario, you want to quickly defog the windshield so that you can be on your way. To do so, you need to follow the below steps:

Step 1: Use the defogger in your car to quickly clear the windshield.

Step 2: When the car is stationary, open all doors if it is feasible. Alternatively, you can crack open the windows. It is advised to carry out this step when the vehicle is stationary because doing so in a moving car would expose you to the winter weather outside. However, if you can brave the elements, carrying out this step in a moving car would be a quicker way to remove moisture from your car’s cabin.

Step 3: As the moisture content inside and outside your car balances out, the condensation on the windshield will reduce.

The idea here is that you want to expel all the moisture from the car’s interior. If you only heat the windshield using the defogger, it will temporarily clear the windshield, but as soon as the temperature in the cabin becomes too hot and you turn off the defogger, the condensation will return. Also, as the air inside the cabin will be hotter, it will be able to hold in more moisture, and the condensation on the windshield could become more severe than before. Therefore, it is important to use a mix of the defogger while reducing the moisture inside the cabin at the same time. You can also switch to the fresh air option, which will bring in colder air with less moisture from the outside into the cabin.

Ultimately by using the above steps, you will find the right settings that will help defog your car’s windshield in the winter months. The actual process will vary from region to region depending on temperature and humidity, but once you have dialled it in, you will be able to defog your windshield in the winter and keep it that way in a matter of minutes.

Tips to defog the windshield from the outside

As discussed before, the windshield fogs up from the outside during the monsoon. It will generally start to fog up once the car has been driven a certain distance. There is a slight chance that your windshield starts to fog up as soon as you start driving, but this only happens when the ambient temperature of your car parking is significantly lower than the ambient temperature on the road. 

Primarily, outside fogging of the windshield happens when excessive air conditioning is used. Over time, it cools down the windshield and as the hot and humid air on the outside comes into contact with the cooler windshield, it forms a layer of condensation on the outside of the windshield. As this kind of fogging generally happens when you are already on the road, it can become dangerous to drive this way, and you need a quick solution to sort it out. Here’s how to go about it:

Step 1: Turn on your windshield wipers. This will wipe away the condensation that is being formed on the outside of the windshield. This is the short-term method to clearing fogging on the outside of the windshield.

Step 2: Once you have your vision back, you need to get started on keeping it that way. In short, you need to equalise the temperature of the windshield and the outside air so that condensation doesn’t occur. A good way to do so is by increasing the temperature of the A/C. It will not work instantly but will equalise the temperature over a period of time. However, once you decrease the effectiveness of the A/C’s cooling effect, it could retain moisture inside the cabin, and the inside of your windshield could potentially fog up as well. Therefore, don’t make drastic adjustments to the A/C temperature, and instead, ramp it up gradually.

Step 3: Alternatively, you can also turn on the defogger to blow hot air on your windshield. This will increase the windshield temperature, and stop condensation from occurring on the outside and inside. However, the hot air from the defogger can make for a stuffy atmosphere inside the cabin, and thus, it should only be used in short bursts.

In the rainy months, there is a lot of moisture in the atmosphere, and if it gets inside your cabin, it has the potential to fog up the inside of your windshield as well. Therefore, it is advisable to drive with the windows up. Furthermore, one should keep dehumidifying agents such as Silica Gel inside the car to absorb the excess moisture.

Ultimately, you will have to use a mix of your wipers while balancing out the temperature at the same time to achieve constant clear vision in the rainy months. It is no easy task, and requires more effort and time compared to the fogging that occurs in the winter months. If you live in an area where achieving this balance is almost impossible because of the atmospheric conditions, you should consider investing in a dehumidifying agent that can be applied on the windshield of your car to keep the fogging away.

Also Read: How To Fill Your Car's Windshield Washer Fluid Properly

What is a Defogger and how does it work in a car?

In the anti-fogging processes that we have described above, we have used the term defogger which can confuse some people. In short, a defogger is a device that helps in removing the moisture from a car’s windshield. To do so, there are primarily two types of defoggers that are used in cars today.

Types of Defoggers

Front windshield defogger: The first type of defogger uses the A/C system to blow hot air on the front windshield. The hot air removes the moisture from the windshield, thus taking care of the fogging problem. This is the most basic type of defogger as well. 

Rear windshield defogger: The second type of defogger is primarily used for the rear windshield and uses thin lines of conductive material that are present in the glass, and can allow high amounts of electricity to pass through them. This process rapidly heats up the windshield and expels away the mist on the glass. This type of defogger is not used on the front windshield as it hampers visibility, however, it is one of the most effective methods to defog a windshield.

Common mistakes to avoid

While a defogger can do a quick job, there are some common mistakes that people make which leads to their cars fogging up more often. To reduce the fogging problem, make sure you are not doing the following:

• You should not not leave sweaty clothes or other such items in a locked car. These clothes have a lot of moisture which can then be transferred to your cabin.
• A lot of people have their cars cleaned everyday. However, few people often air out its interior on a warm sunny day. Doing this on a monthly basis can eradicate the build up of moisture inside a car’s cabin, which will reduce the intensity of fogging.
• One must learn how to correctly use the recirculation mode in a car properly. If you have more people in the car, it is better to switch to fresh air, as it helps to better expel the moisture emitted by the occupants.
• Many car owners clean their windshields from the outside, but forget to clean from the inside. The dirt and grime on the inside can attract moisture and increase the chances of fogging.

Conclusion

As we initially discussed, clear vision is crucial for safe driving and fogging has the potential to disrupt that. However, by using the techniques that you have learned, you can achieve a clear windshield. It is important to note that the process will be slightly different for everyone as atmospheric conditions change from region to region. Also, going from one car to another can also require a little tweak to the process. Finally, modern cars are equipped with highly capable HVAC systems that can automatically maintain a set temperature inside the cabin. These systems are also great at keeping a clear windshield, and it is only in extreme weather conditions that you will have to use the techniques mentioned in this article to clear your windshield, if your car has an automatic climate control feature.

FAQS

Q. How do you quickly get rid of the fog on your car’s windshield?

You can quickly get rid of the fog on your car’s windshield by using the defogger function.

Q. How to defog a car’s windshield during rain without using A/C?

To defog a car windshield without A/C, you will need to use an anti-fogging product on the windshield and also position dehumidifying agents such as Silica Gel inside your car.

Q. How to defog a car windshield in the rain?

To remove the fog on the outside of the windshield, you need to use the wipers. To remove fogging on the inside of the windshield, you need to use the A/C. However, using the A/C for too long will lower the windshield temperature, which will promote fogging on the outside.