2013 Toyota Tundra Regular Cab Owners Manual - Page 280
2013 Toyota Tundra Regular Cab Manual
Page 280 highlights
3-1. Using the air conditioning system and defogger Vehicles with a manual air conditioning system On/off Press the button to turn on the back window defogger. The indicator will come on. The defoggers will automatically turn off after about 15 minutes. Pressing the button again also turns the defogger off.