Amana refrigerator too warm, freezer works.

[Slee]

Hi, I have an Amana, bottom freezer refrigerator that has developed the problem of the refrigerator being too warm. I searched posted threads and, following the advice I got there. I took the back panel off and confirmed that the fan was running. It is. Then I left it unplugged overnight to make sure that it was completely defrosted and plugged it back in. It worked for approximately two days and now I am faced with the same problem again. It is only about six years old and since the freezer still works I hate to just discard it. Is there anything I can do or check?