1998 Oldsmobile 88 Owner's Manual - Page 131

Rear Window Defogger Press the rear window defogger button to warm the defogger grid on the rear window. The indicator light will glow while the rear window defogger is operating. NOTICE: Do not try to clear frost or other material from the inside of the rear window with a razor blade or anything else that is sharp. This may damage the rear window defogger grid. The repairs wouldn't be covered by your warranty. Ventilation System The defogger willturn off automatically after about 10 minutes of use. If you turn it on again, the defogger will operatefor about onlyfive minutes. You can also turn off the defogger by turning ignition to OFF or the pressing the rear defogger button on your system again. Do not attach a temporary vehicle license across the defogger grid on the rear window. Your vehicle's flow-through ventilation system supplies outside air into the vehicle when it's moving. Outside air or will also enter the vehicle when the heaterair conditioning fan is running.