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Poor cooling is often the result of a heavy frost build-up on the evaporator coils or a condenser that is clogged with dust, lint, and dirt.
Evaporator coils poor cooling is often the result of a heavy frost build-up on the evaporator coils. You can't see these coils without removing a panel on the inside of your freezer. A sure sign that there is a build-up is the presence of any frost or ice build-up on the inside walls, floor, or ceiling of the freezer. Such a frost build-up usually indicates a problem in the self-defrosting system or damaged door gaskets.
You should look inside the freezer at the back wall. Remove the inside back wall of the freezer (part 4 below).
If you see -
Light even frost - Good, evaporator (part 12 above) is working correctly.
Heavy even frost/ice - BAD, defrost system is not working correctly.
Heavy frost/ice in one small area - VERY BAD, you may have problem with sealed system and/or compressor. Recommend purchasing new refrigerator.
The refrigerator is supposed to self-defrost approximately four times in every 24 hour period. If one of the components in the self-defrosting system fails, the refrigerator continues to try to cool. Eventually, though, so much frost builds up on the evaporator coils that the circulating fan can't draw air over the coils. There may still be a small amount of cooling because the coils are icy, but with no air flow over the coils, cooling in the refrigerator compartment is quite limited.
Here's an inexpensive, though inconvenient, way to determine if the problem is with the self-defrosting system. Remove all of the perishable food from the refrigerator and freezer, turn the thermostat in the refrigerator to Off, and leave the doors open with a fan blowing air into the freezer for 24 to 48 hours. (Be sure to have several towels ready in case the melting frost and ice causes the drip pan to overflow). You can speed up this by carefully using a hair dryer. This allows the refrigerator to defrost "manually."
When the entire refrigerator is at room temperature and there no frost or ice, plug the refrigerator in and the thermostat back to a normal setting. If the refrigerator then cools properly, it indicates a problem with one of three components in the self-defrosting system:
The defrost timer
The defrost thermostat (also called the bi-metal switch)
The defrost heater
If it still does not cool properly, there may be a problem with the refrigerant level or the compressor. Recommend purchasing new refrigerator.
Let me know if you would like more information or clarification.