1996 Chevrolet Suburban Owner's Manual - Page 162

Rear Window Defogger (Option) You can tell if your vehicle has this option by looking at the rear window. If you see lines running across the glass, you have it. These are the wire-like elements which heat your window. NOTICE: Scraping the insideof your rear window could cut and damage the defogger. Your warranty would not cover this damage. And, don't put decals there, you might have to scrape them off. For best results, clear the window of as much snow or ice as possible first. To turn on the rear window defogger, press the rear defog button next to the fan control knob. The rear window defogger will only work if the ignition switch is turned to RUN. 3-7