Wrapped around the coils behind that panel in the freezer is the defrost heater arrowed blue in the top diagram. Disconnect that heater, set your meter to any ohm setting. If you get a reading its good. Any reading is ok. No reading is bad, replace the heater.
Arrowed red is the the defrost thermostat. This part must be frosty white cold to test. It will not read unless it is. Frosty cold for the defrost thermostat is any ohm reading is good, no reading is bad.
The test for the board is to verify the heater and thermostat is good. That leaves the board as the bad part. One of the 3 defrost parts is bad and if you test 2 that test good by elimination the board is bad. That is the way its tested. The board is located in your fresh food section at the top and the buttons you press to adjust the temperature are actually attached and are part of that board. I have arrowed it red and is in the lower diagram. To replace any of these parts you need to unplug the unit and change them out.
The board is different. You will have a sheet to follow and a code to enter to program the board. There is a sticker in your fresh food section with your model and serial number. On that same sticker you will find the word code followed by four numbers. Thats your code.
The top diagram arrowed blue is the defrost heater.
Arrowed red is the defrost thermostat.
In the bottom diagram is arrowed the control board.
The heater is factory part number 12729128
The defrost thermostat is part number 12639324SP
The control board is factory part number 12868513
That should get you well on the right track. If you have questions please ask.
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