What is the sign that the defrost system is not working. These systems are normally quite simple. They consist primarily of a defrost timer, which on most refrigerators initiates a defrost cycle every twelve hours; a bimetal limit switch to turn the heater off when the evaporator-plate reaches a level above 60 degrees; and the heater itself, which he embedded within the evaporator coil or located immediately attached to it. (Remember that some models use the “hot gas,” as previously mentioned.
An initial check of this system from Smith’s Appliance Repair of Smyrna is to simply turn the knob of the defrost timer to the point where you hear the system click into the defrost cycle. If the heating element is working, you will probably able to hear a slight “popping” as it expands from the heat, a hiss as a drop of melting water strikes the warm heater. If the heater sounds as though it is working, allow the timer to stay in the defrost position. It should end the defrost cycle and turn the compressor back on within a maximum period of twenty-five minutes. If it does not, suspect the defrost timer. The small synchronous motor may not be working. On many timers the motor movement may be observed through a small window in the back of the cover. Both switch contacts may be tested with the VOM. A single-pole, double-throw switching arrangement is often used on these timers a circuit to the compressor is established during the running circuit to the heater during the defrost cycle. Both circuits can be energized at the same time.