Toyota Lexusc Owner's Handbook Manual page 80

Even if the wiper lever is in the "AUTO" position, the system will
switch to intermittent operations in the following conditions:
D When the windshield gets extremely cold (at less than
–10_C or 14_F)
D When the system malfunctions
However, when the windshield gets extremely hot (at more
than 90_C or 194_F), the wipers do not operate even if the
wiper lever is in the "AUTO" position.
When the ignition switch is turned off with the wiper lever in the
"AUTO" position, and then the ignition switch is turned on
again, the automatic operation may not work even if raindrops
are on the windshield.
In this case, move the lever to another position and return it to
the "AUTO" position again.
NOTICE
Do not apply detergent to or wet the automatic wiper
control sensor when cleaning the inside of the
windshield.
CAUTION
Be careful not to get your fingers caught between the
wipers and windshield.
When the wiper lever is in the "AUTO" position with the
ignition switch on, the wipers
automatically in the following cases:
D If you touch the upper center of the windshield
adjacent to the sensor.
D If you wipe the upper center of the windshield
(adjacent to which the sensor is located) with a towel.
D If the windshield vibrates.
D If you touch the sensor.
SWITCHES
could operate
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