Defrost Circuit Problems
If you have a defrost circuit problem its not too serious. Its usually just one of 3 components are worn or burnt out. Here are some answers to commonly asked questions about defrost circuits that use a mechanical timer:
Many newer refrigerators built since 1997 use an adaptive defrost module, a subject that the new fourth edition of the Fridge Doctor Book covers. However, before this they used a defrost timer to cycle. Here is some basic information about automatic defrost using a timer from The Fridge Doctor Book:
As the air that is circulated by the fan inside the freezer passes through the fins of the freezer coils, moisture in the air turns to frost and deposits on the fin surfaces of the freezer coils. If this frost was allowed to accumulate, eventually it would build up to a point where the air would no longer circulate. All refrigerators need to be defrosted some way or another. The Standard Frost Free does this automatically. Here is how it works:
Included in the wiring circuit, is a defrost timer (most timers now work on a six hour cycle, so for the purposes of this discussion we will assume six hours). Every six hours, or six hours of compressor run time depending on how it is wired into the circuit, the timer switches off the current to the running devices associated with the compressor and provides current to an element embedded in the freezer coils. This is more graphically illustrated in the wiring diagram on figure 2.5. Once the timer has clicked into the defrost part of its cycle, the main defrost element will stay on until the defrost timer reaches the end of the defrost part of its cycle (about twenty minutes), or until the temperature in the freezer coil rises above the set level of the defrost thermostat, also attached to the freezer coils.
Figure 2-5 Standard Frost Free wiring diagram with mechanical defrost timer
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