My freezer iced up. After I manually defrosted it and turned it back on, my freezer is -10 and fridge is 30 degrees, with settings at 0 and 36 on control panel. Then, freezer freezes with ice again after a month and blocks airflow to fridge, which then gets warm. This has happened several times, now. I believe the thermostat may be the culprit. Can you help me locate and troubleshoot the thermostat?