Those thin stripes across your rear window are actually tiny electric heaters, engineered to clear frost, ice, and condensation without blocking your view. When you press the rear-defroster button, current flows through these resistive strips, generating gentle, even warmth across the glass. That’s why you’ll often see the window clear in neat horizontal bands. Many vehicles also tie this system to heated side mirrors, improving visibility where you need it most in bad weather.
Because the grid is printed or bonded onto the glass, it’s more fragile than it looks. Aggressive scraping, metal tools, or abrasive cleaners can scratch or break a strip, leaving a stubborn foggy band that never clears. The good news: a single damaged line doesn’t doom the whole window. Conductive repair kits or a technician can often restore function. Treat those lines carefully—they’re a small, silent safety system standing between you and what you can’t see coming.