The part(s) or condition(s) listed below for the symptom Freezer defrost drain frozen are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
The drain strap may have fallen off or deteriorated. Some freezers have a small copper or aluminum strap that attaches to the defrost heater and extends into the defrost drain. When the defrost heater turns on, heat is conducted through the drain strap to melt any ice that may have accumulated in the defrost drain. If the drain strap is defective, it will not be able to melt the ice, causing the defrost drain to frost over.