A defrost timer allows a refrigerator to get rid of unnecessary frost build-ups which can occur inside the freezer and/or refrigerator compartments. The timer attaches to heater coils which melt the frost for collection for a certain amount of time. Once the timer goes off, the circuit connecting to the coolers comes back into play. Depending on your refrigerator model, your defrost timer may be located in different locations.
Remove the refrigerator kick plate. The kick plate appears as a grill on the bottom of your refrigerator. Many refrigerators situate the defrost timer safely behind the bottom grills which protect it from damage. You'll find the defrost timer as a small protrusion sitting right behind the grills.
Open your refrigerator's door and look at the control panel for a small side attachment that looks like an electrical box. If you see one, you found your defrost timer.
Unplug your refrigerator and turn it so that the back is exposed. You don't have to turn it a full 180 degrees, but just enough for you to have the flexibility to look at the back side. Look for a protruding box with four pins leading to it. If you see this, you found your defrost timer.