The defrost thermostat / bi-metal protector is a thermal cut-off that will break connection to the heater if the unit becomes too warm. These are typically a thermostat of last resort, so if continuity dies, the heater is rendered totally inoperable, and a new unit needs purchased before the heater can run again properly.

DA47-00243K contains one harness and a longer length from the harness connector to the thermostat.