(Condensed Re-print from The Samurai Appliance Repairman at http://appliantology.org/)
A common problem with refrigerators is various forms of water in places where it shouldn’t be. Such as: water at the bottom of the freezer and running out the door in a side by side refrigerator; frost built up on the back wall of the freezer compartment; moisture on glass bottles and jars on the side walls inside the refrigerator compartment; or a solid slab of ice on the bottom of the freezer compartment.
Water in the refrigerator takes three forms: ice, frost, and condensation.
Condensation appears as “sweating” on jars, bottles, and even the sidewall in the refrigerator compartment. It’s caused by water vapor condensing into a liquid state when it contacts cold surfaces inside the refrigerator. This means outside, humid air is getting into the refrigerator. Look for bad gaskets, doors not closing properly, or doors left open.
Ice is water that froze into a solid. It’s an important distinction from frost, also known as rime ice, that fuzzy looking stuff that’s formed when water vapor condenses directly into a solid, bypassing the liquid state. Ice and frost are the effects of two completely different causes.
If you see smooth or solid ice in a freezer, you’re looking at liquid water that flowed, pooled and froze: Such as a clogged condensate drain in the drip trough below the evaporator coil; ice maker fill tube leaking or out of place; ice maker mold leaking.
FROST OR RIME ICE
If you see frost or rime ice in a freezer, you’re looking for water vapor that’s getting into the compartment. How does water vapor get into a refrigerator? It comes in with the outside air. In most cases when you see frost in a freezer, you’re looking for an air leak: bad door gaskets or doors not closing all the way.
A common problem is frost accumulated on the evaporator coil or back wall inside the freezer that covers the evaporator coil. This is a defrost system failure (defrost terminator stuck open, burned out defrost heater, bad defrost timer (on older units) or adaptive defrost control (ADC) board).
The reason rime ice forms on the evaporator coil in the first place is because the coil operates at a temperature of -20F. At that temperature, water vapor that contacts the coil will condense and freeze directly into a solid, forming rime ice. Every few hours the defrost system should kick in and melt that ice, because if it’s allowed to accumulate it will eventually act as an insulator, preventing the air from contacting the evaporator coils and getting cold. The resulting problem would first be seen as a warm refrigerator compartment and, if allowed to continue, eventually the freezer will also get warmer than normal (normal = 0F). Rime ice accumulated on the inside of the back wall in the freezer will often be seen at this point.
This melted rime ice has a special name: condensate. (Not to be confused with condensation, although the words are similar, they arise from two different causes.) Condensate refers to the water that gets melted off the evaporator coil in the freezer compartment during the defrost cycle. This condensate drips onto the condensate drip trough below the evaporator coil and drains out the condensate drain– a hole in the condensate drip trough– through a tube to the drain pan placed down by the compressor where it eventually evaporates due to the combined action of the compressor heat and condenser fan motor.