Lexus GX470 2004 Owner's Manual page 54

Twist the automatic control adjuster in the "–" direction to
lower the sensitivity, and the "+" direction to boost the
sensitivity.
The sensor is on the inside of the windshield as shown above.
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.
If you stop the vehicle with the wiper switch in the "LO" position,
the wiper speed automatically changes from low speed to
intermittent operation speed.* This function does not work
when the automatic control adjuster is in the "+" position.
NOTE:
* This feature can be deactivated.
Ask your Lexus dealer for details.
SWITCHES
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