Freezers have a defrost cycle with heating elements. This is controled by a defrost timer. This timer is often located by the temperature controls or behind the floor panel/grill. It has a turn "knob" that uses a regular screwdriver to move the timer forward. You should hear it click as you turn it 8hours forward into the 15minute defrost mode. You may need to fast forward it a couple times to defrost excessive ice... and be prepared for water to dribble out, 'cause the drain may be iced up also... which could also be the original problem(?). If you can't find the bad defrost timer, look for the schematics hidden behind that floor grill or on the back of the frig.
mike
September 2007