The evaporator coil on a refrigerator is generally located in the back of the freezer compartment. It is responsible for helping cool the interior of the refrigerator to the proper levels. Sometimes when there is a problem with the unit, ice can accumulate on the coils and reduce the refrigerator's ability to cool. When the freezer ices up and the coils are covered in ice, there can be several causes.
Most icing problems in the evaporator coils are linked to the defrost system. The self-defrosting refrigerator typically defrosts at somewhat regular intervals several times per day to keep frosting from turning into icing. When the defrost mechanism fails in any way, the ice begins to accumulate. One component of the self defrost system is the defrost timer, which regulates when defrosting occurs. It tells the defrosting system when to turn on and off to get the desired results. If this part of the system goes bad, the defrost will not turn on at all, which results in over frosting and eventually ice buildup.
Another reason the self-defrosting system may not work is a problem with the defrost thermostat. This part of the system monitors the temperature around the evaporator coils and lets the timer know when to defrost. If the thermostat is not reporting accurate information, or not reporting at all, the timer doesn't tell the defrost system to do its job and ice accumulates.
The workhorse of the self-defrosting system in the refrigerator is the defrost heater. Heat is needed to melt away the frost that naturally accumulates on the evaporator coils as the refrigerator operates normally. When the temperature gets low enough in the compartment, the thermostat tells the timer to turn on the heater. The heater warms up and begins to melt the frost away. The frost drains into a catch pan in the bottom of the refrigerator. If the heater malfunctions, the frost does not melt away and ice forms.
If your evaporator coils are truly full of ice, the door gaskets are not likely to be the problem, but long-term neglect of cracked or worn out door gaskets could be the cause in some cases. When outside air is allowed to enter regularly through poor seals in the freezer door and warmer air creeps in, the freezer compartment walls may begin to ice up. Eventually this could lead to coil icing, although a buildup of frost on the walls is more common with this problem. Replacing the gaskets will help stop the problem and lower energy use.
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