1995 GMC Yukon Owner's Manual - Page 167

The rear control works just like the front control. It will allow second seat passengers to adjust the controls as they desire. Rear Window Defogger (Option) You can tell if your vehicle has this option looking at the rear by window. If you see lines running across the glass, have it. These are the wire-like you elements which heat your window. NOTICE: Scraping the inside your rear window could cut and damage of the defogger.Your warranty would not cover this damage. And. don't put decals there, you might have scrape themoff. to For best results, clear the window as much snow or ice possible first. of as 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