TOYOTA 2011 Tundra - Manual (Page 330)

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3-1. Using the air conditioning system and defogger
CAUTION
n To prevent the windshield from fogging up
Do not set the air outlet selection dial to during cool air operation in
extremely humid weather. The difference between the temperature of the
outside air and that of the windshield can cause the outer surface of the
windshield to fog up, blocking your vision.
NOTICE
n To prevent battery discharge
Do not leave the air conditioning system on longer than necessary when the
engine is stopped.