2011 GMC Savana 3500 Passenger Owner's Manual - Page 204

8-4 Climate Controls Notice: Do not use a razor blade or sharp object to clear the inside rear window. Do not adhere anything to the defogger grid lines in the rear glass. These actions may damage the rear defogger. Repairs would not be covered by your warranty. < (Rear Window Defogger): Press to turn the rear window defogger on or off. The rear window defogger turns off several minutes after the button is pressed. If turned on again, the defogger will run for several more minutes before turning off. The defogger can also be turned off by turning off the engine. Do not drive the vehicle until all the windows are clear. Rear Heating System For vehicles with a rear heating system, it lets you adjust the amount of air flowing into the rear of the vehicle, from the front-seating area. This feature works with the main climate-control system in the vehicle. AUX: The thumbwheel for this system is located in the instrument panel switchbank below the audio system. 9 (Fan): Turn the thumbwheel up or down to increase or decrease the amount of heated air sent to the rear-seating area.