I have an old refrigerator, so perhaps it's not salvageable, but I would like to give it a try.

Yesterday I found top shelves in both freezer and refrigerator sides properly warm, at the same time on the bottom shelves on both sides everything was fully frozen. I disconnected refrigerator overnight and turned it on this morning, which didn't help, same situation top warm, bottom cold.

Can someone help identify what could be wrong, or is there a way for me to run some kind of test.