Those lines heat your rear window

The thin brown or orange lines on your rear window are part of a defroster system. When turned on, electricity runs through them to warm the glass and clear fog, frost, and light ice.

How the defroster system works

Electricity heats the thin wires in the glass when you activate the rear defroster. Some vehicles also heat side mirrors with the same button. Always run the engine before using the system.

“Make sure the engine is on before operating the heated rear windows.”

Why front windshields work differently

Front windshields clear using warm air from the heating and ventilation system, so they don't need visible heating lines. Some heated windshields exist with very fine wires built into the glass.

Sharp tools can damage the lines

The thin defroster lines are fragile and can be damaged by scratches, sharp tools, rough cleaning, or removing decals. A break in one line leaves a strip of fog behind while the rest clears.

“Do not use harsh chemicals, razor blades or other sharp objects to clean or remove decals from the inside of the heated rear window.”

Not all lines are defroster wires

Some vehicles have radio antennas built into the rear window glass. Upper lines may serve as AM/FM antennas rather than defroster elements. Check your owner's manual to identify which lines do what.

When the whole system fails

If no lines heat up at all, the problem may be elsewhere in the defroster system rather than the lines themselves. A single broken line won't disable the entire rear window.