1999 Subaru Impreza Owner's Manual - Page 129

Rear window defogger switch D Do not use sharp instruments or window cleaner containing abrasives to clean the inner surface of the rear window. They may damage the conductors printed on the window. D To prevent the battery from being discharged, do not operate the defogger continuously for any longer than necessary. The rear window defogger operates only when the ignition switch is in the "ON" position. CAUTION Indicator light HS0063 To turn on the defogger, push the switch. To turn it off, push the switch again. The indicator light located on the switch lights up while the rear window defogger is operating. The defogger will automatically shut off after about 15 minutes. If the window clears before this time, push the switch to turn it off. It also turns off when the ignition switch is turned to the "ACC" or "LOCK" position. If defrosting or defogging is desired when you restart your vehicle, you have to push the switch to turn it on again. 3-24