I have been replacing parts, but have not found root cause. The temp on freezer was subzero, and frig was not cooling - replaced temperature sensor, ice maker switch. Read blog, played with damper and loosened it. Coils on freezer have frosted and do not want to defrost (unplugged for a couple of days and replugged in - frosted again). It may be a loose wire as can hear fan turn on when I unscrewed protection panel in back of freezer. Can not find how to manually turn on defrost cycle.