Locate the defrost timer in your refrigerator. You may have to consult the user guide for your particular refrigerator in order to determine the location. Generally speaking, the defrost timer can be found behind the cold control cover, near the bottom corners at the rear of the unit, and in the ceiling of the refrigerator.
Insert your flat-head screwdriver into the groove in the timer wheel and turn the wheel slowly clockwise until the cool air shuts off. The defrost heater will then turn on. Leave the fridge in defrost mode until the vents are defrosted. If you cannot locate the defrost timer, proceed to the next step.
Unplug your refrigerator from its power source.
Plug a hair dryer into a nearby outlet and turn it on. Place the dryer over the vents inside the refrigerator and hold it there until the vents are defrosted.