Alarm sounding kenmore 253 freezer - Kenmore 20.3 cu. ft. / 575 liter Upright Freezer 23024

SOURCE: Kenmore upright freezer alarm sounds constantly

replace the battery in the grill or the hi-voltage control under the unit in the back

SOURCE: Kenmore Upright Freezer Model 253-9280810

is it possible the door has not been closed at some point?
If so they can build up with ice in the evaporator which the defrost system cannot handle....Try a manual defrost.
Depending on where the unit is installed high ambient temperature can drop the internal temp enough to set the alarm off though they will still freeze sufficiently