Unplug the refrigerator from the wall outlet.
Open the refrigerator's fresh food cavity door and remove the screws from the bottom of the control housing, which contains the temperature controls and is located on the roof of the fresh food cavity.
Lower the control housing away from the roof of the fresh food cavity.
Pull the timer out of the control housing. The timer can be identified as it is a rectangular box with four terminals on the bottom. Compare the new timer to the old timer if you are unsure of the correct component.
Pull the wire harness off of the bottom of the old defrost timer and discard the timer.
Connect the wire harness to the new defrost timer.
Place the new timer in the control housing and press it firmly into position.
Resecure the control housing to the roof of the fresh food cavity using the screws that were removed.
Plug the refrigerator back into the wall outlet.