Frigidaire FEC180WH00 Owner's Manual page 13

In sleep mode, the indicator of the fan speed changes when the
natural mode switches. For example: when the sleep mode is
turned on at medium speed, it will switch to low speed natural
wind automatically after 30 minutes. At this point, the medium
speed indicator turns off, and the low speed indicator turns on.
OTHER FUNCTIONS
a. Automatic dim function: If there is no button operation in 1
minute after any indicator is on, the indicator will
automatically dim (33% of the original brightness). The
indicator will light up again if any button is pressed after 1
minute of no operation.
b. Uninterrupted memory function: If it isn't the first time that
the unit is turned on, the unit starts with the state before
shutdown.
AUTOMATIC SHUTDOWN FUNCTION
When the unit is turned on and the timer is disabled, it will shut
down automatically after 15 hours of continuous operation from
the last button operation.
If you want to cancel this function, press and hold the
for 3 seconds, and the buzzer will beep to notify you that the
automatic shutdown has been canceled. To restore the automatic
shutdown function, press and hold the
seconds.
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button for another 3
button