More often than not, you have broken defogger grid lines. All of those lines in your rear windshield are not there for looks. They are actually thin metal strips that are heat-activated by your car when you depress the rear defogger button or turn on the rear defrost.
The lines can be scratched and separated, causing them to work elsewhere on the windshield, but not in the broken spots. The areas that are scratched or broken then leave big frost spots. Thankfully, you will not need a windshield replacement unless the windshield is also severely cracked. If you're ready to drive safer on the road, here is how to fix the broken grid lines.
Kits for Repair
Luckily, this is an easy repair, even easier than using a resin to fill in a chip in your windshield. Each repair kit contains filament, tape adhesive, and the tools needed to make this repair. The metal filament helps breach the scratch or break in a grid line, while the tape adhesive helps the filament adhere to the window. A gentle pressing of the tape and filament to the window, followed by lightly cutting away the excess tape, and the grid line is repaired.
The downside to these kits, however, is that they can only fix small scratches and breaks in the grid lines. If you have one giant break or a major removal of a grid line, you will need an auto glass specialist to fix this. An entirely new grid line has to be professionally applied, often by removing the rear windshield to apply the line while the windshield is laying on a flat working surface.
A Word on Cracked Windshields and Defogger Grid Lines
In the event that your rear windshield acquires a crack, it will interrupt the flow of the heat transfer through every defogger grid line through which the crack passes. Additionally, the frost, rain, ice, and snow can seep into this crack and cause the crack to expand when the frost, ice, or snow melt from the heat of the defogger. You should get the crack repaired right away, or your defogger will be unable to clear your rear windshield properly.
If you continue to experience foggy window spots that make your morning commute difficult, contact services that provide windshield replacement or repair. They can either provide the kids mentioned or they can do this work for you.