Most of us have noticed our car windows all fogged up on cold mornings. This is caused by moisture trapped inside the vehicle which then condenses into small drops of water on the glass. If the air outside is colder than the inside, the droplets will form on the inside of the glass. As soon as you enter the vehicle, your breath will add heat and more moisture to the air which fogs the windows up even more. The wipers can’t help clear up the fog on the inside of your car, for that you will have to use the defrost setting on the climate control. For the windshield, vents located right below the glass direct the air to the window to clear it up. Commonly the air conditioning will engage to help get rid of the moisture as the A/C dries the air before it goes through the air vents. The drier air is absorbs more moisture and clears the window faster than with normal air. On the rear windows, wires are placed on the glass in a grid pattern. These are the black lines commonly found on the rear windows. Electricity gets sent through the wires which generates heat and clears the moisture from the window.
What the defrost indicator light means
Whenever the light is illuminated, the defroster is turned on. The symbol for the front is a curved window, while the rear is rectangular. While you are defogging the windshield, you may not be able to get air out of the normal vents. This way all the air is forced up to try and clear the moisture so that you can drive safely. Any flashing with these indicators means a problem has been detected. You will need the help of a professional with a diagnostic scan tool to read the code saved on the computer. This code will help identify any issues that are present. Depending on the problem, you may or may not be able to use the defroster. Some vehicles with automatic climate control can turn on the defroster when the humidity gets too high. This will help keep you windows clear and you shouldn’t have to do anything. If your vehicle has this feature it is normal for the light to illuminate occasionally while you are driving.
Is it safe to drive with the defrost indicator light on?
The defroster keeps your vision clear while driving and without it, you could have a really difficult time seeing out of your windows. If the edges of the windows start to fog up, turn on the defroster for a little bit before the fog covers the whole window. Even with a malfunction detected, so long as you can clear up the windows, you can still use the car normally.
If you are experiencing any issues with your defroster, our certified technicians are available to help you diagnose any problems.
This article originally appeared on YourMechanic.com as What Does the Defrost Indicator (Front and Rear) Warning Light Mean? and was authored by Spencer Cates.