The defrost timer is usually found behind the front grill of the freezer. It may also be found behind a cover plate inside the freezer, in the temperature control console, or behind the freezer near the compressor.
Before replacing the defrost timer, unplug the freezer to avoid an electrical shock hazard.
The timer is usually held in place with one or more screws. Remove the screws and gently pull the timer out far enough to disconnect the wiring connector.
The connector can be removed by firmly pulling and rocking it left and right. It is not necessary to note the position of the wires because the connector plug is keyed so that it can be replaced in only one way.
Connect the wiring connector to the new timer, refasten the timer in place, replace the cover and plug in the freezer.