Toyota 2008 Prius Quick Reference Manual page 246

3-2. Using the air conditioning system and defogger
n Operating conditions
The "POWER" switch must be in the ON mode.
CAUTION
n When the outside rear view mirror defoggers are on (vehicles with mir-
ror defoggers)
Do not touch the rear view mirror surfaces, as they can become very hot and
burn you.
NOTICE
To prevent 12 volt battery discharge
n
Turn the defoggers off when the engine is not running.
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