I have a Frigidaire refrigerator model F44N21C. The refrigerator nd the freezer are not cooling to where they need to be. Last night the freezer would not freeze ice in the tray other than a light layer. I defrosted the frig at 6 am this morning and restarted it at 12:30 pm. The unit is only cooling the frig to 36 degrees and the freezer to 33 degrees. The fan in the freezer does run and there is no frost behind the back panel inside the freezer. What wrong?