The horizontal stripes across most rear windshields form an electrical heating grid, typically printed onto the inside surface of the glass. Press the rear defroster button, and current passes through these conductive tracks, producing warmth that clears condensation and melts frost. Unlike the airflow commonly used to clear the front windshield, this system heats the rear glass directly. Many vehicles switch it off automatically after several minutes to limit unnecessary power use.
That useful grid deserves gentle treatment. Abrasive pads, sharp tools, or careless removal of stickers and window tint can break its delicate tracks, leaving bands of glass uncleared. Clean the interior rear window with a soft cloth and avoid scraping across the lines. If one track stops working, a suitable conductive repair kit may restore a small break; broader failures need diagnosis. Before driving, make sure your windows are clear—working defrosters help, but visibility comes first.