Lexus 2004 GX470 Owner's Manual page 248

You can adjust the temperature within "10_F ("5_C)
which compared with the temperature setting of the front
air conditioning. Push the left side of the button to lower
the temperature, and push the right side to raise the
temperature.
NOTICE
To prevent the battery from being discharged, do not
leave the rear cooler on longer than necessary when the
engine is not running.
AIR CONDITIONING
233