How To Defog My Windshield With AC

By Nidhi Nangia. Updated: January 20, 2017
How To Defog My Windshield With AC

On rainy and cold days, it is very common for your car windshield to fog. Due to this, you lose visibility of the road ahead, and put everyone’s life in the car at risk. The difference between humidity and temperature inside and outside the car is the major factor that contributes to fogging. In addition to the cold glass, the outside’s contact with the inside temperature also leads to fogging on the windshield. When the outside air comes into contact with your windshield, it emits steam and produces condensation. If you have AC inside your car, then this difference between the temperatures becomes bigger, and the fogging stronger. We have already told you How To Defog A Car Windshield In Seconds. Here at, we will tell you how to defog my windshield with AC.

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Steps to follow:

One way to defog your windshield with AC is to increase the temperature of your windshield by blowing warm air inside the car. You can do this by using your car’s heater and defogging vents on the bottom of the windshield. This is an excellent way to remove outside glass condensation under humid climatic conditions.

How To Defog My Windshield With AC - Step 1

If outside humidity is lower than that inside the car, then it means that the people inside the car are releasing excess water and moisture. To handle this, you can reduce the inside water content by opening a car window or opening all car windows a little bit. Doing this will quickly reduce the dew point inside the car, and allow the fog to dissipate.

How To Defog My Windshield With AC - Step 2

You can defog your windshield by turning on your AC systems. This also works as a dehumidifier. That is why most cars turn on their AC systems automatically when you switch to defrost setting. If you want warm air inside your car, then the AC will first dehumidify the inside air, and then warm it up by heater. Remember, applying cold air on your windshield will eliminate the moisture more slowly. This is because cold air cannot hold as much water as warm air.


If you have water condescension on your windshield, the quickest solution is to open a window, select defog, defrost or demist vent, high fan, and high heat, and turn on your AC compressor. Some cars automatically turn it on when you select the defogging vent. This step works in all situations, but you may make the necessary changes as per the climatic conditions you are driving in, and the capacity of your car.


To defog your car’s windshield quickly, allow the outside air to freely circulate inside the car. Lower down some of the windows of your car, so that the outside air enters inside the car. By doing this, you will allow the inside and outside air, humidity and heat to mix with each other. With this step, the car will be defogged completely and quickly.


Make sure that your car’s engine is at a temperature of 90˚C approx, which will allow the windshield to defog quickly and properly. If you have air conditioning in your car, it will become easier for your windscreen to defog. You should not wipe the mist off the windscreen, as this will reduce visibility by making the glass streaky and dirty in the long run.

How To Defog My Windshield With AC - Step 6

If you want to read similar articles to How To Defog My Windshield With AC, we recommend you visit our Car Maintenance and Repair category.

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