Originally Posted by bwheeler
My Amana refrigerator is about 5 years old. Today I opened the freezer to get something out and noticed food was starting to thaw. My refrigerator has a bottom freezer. Also the back wall of the freezer was frosted over.
It's most likely a failure of one of the automatic defrost components -- the defrost timer, the defrost heater element, or the defrost thermostat. If any one of them fails, the evaporator coils won't get defrosted every 6-8 hours as they should and quickly get clogged with frost. Once they are clogged, cold air can't flow past the coils and circulate, so the freezer and fresh food sections tend to get warm.
If you're willing and capable of doing the work yourself, the parts will cost somewhere in the range of $140-$200, if all need to be replaced; the defrost heating element is typically the most expensive, running around $60-$70 from an appliance parts store, followed by the defrost timer. If it's just one part, such as the defrost thermostat, it can be purchased for less than $20. Some newer refrigerators use an electronic "motherboard" that controls all functions in the refrigerator, and instead of a defrost thermostat, these units use a thermistor, not likely to fail. If the defrost heater element checks out OK (it should have a resistance reading in the range of 10-40 ohms), then one would need to replace the entire motherboard.