on the back side of the heater control panel
If it is around '96, the switch is on the dash panel, left side of the steering wheel. Should have a timer on it also.
if defrost timer not working properly, refrigerator will be in continuous run.
The defrost timer is located behind the light panel in the ceiling of the fridge compartment. There are two screws that hold it against the plastic plate it sits on and hold the timer wheel against a hole in that plate which lets you advance it with out having to remove it.
To GE model GSSxxxx models, there is no defrost timer. It uses the main control board to time it.
At the bottom of the refrigerator, in the front, behind the grill. It is retained by a 1/4" screw to a metal plate. The timer is behind the metal bracket or plate.
More than likely its the defrost timer or the defrost heater. You can try and advance the timer which is usually located at the top of the refrigerator compartment. Its usually a small round circle with a slot in the middle. Take a slotted screwdriver and advance it till you hear it click then stop advancing it. This more than likely is defrost mode. It should kick on the defrost heater. Listen closely if you can hear the heater kicking on and sizzling the ice. If you do advance the timer to run after about 1/2 an hour and repeat the process until the ice is gone. If this works then the timer is defective and needs replaced. If this process doesn't work then the defrost heater is probably defective.
the timer
the defrost timer is part of the circut board that has your ice cube selector switches on it..rite above where the ice comes out on the outside of the freezer door..
The outside unit will not defrost and a thick layer of frost will build up, rendering it innefective.
the clicking you hear is more then likely just a noisy defrost timer..in some ge refrigerators the defrost timer is mounted close to the temp control.
It is possible that the defrost timer is bad or that there is a leaking gasket on the door. IF the frost appears far in the freezer, it is probably the defrost timer. If the frost is built up near the inside edges of the door, the gasket is loose or bad
The defrost timer sometimes is built into the main board