What role does the thermostatic switch [defrost bimetal] play in the defrost cycle? What should be it's condition at room temp? What low [how low?] temp?
The defrost bimetal is used as a metering device to terminate the defrost once the temperature reaches 50 degrees. At room temp the defrost bimetal should be in an open state. At below 50 degrees the bimetal should be closed. It works in conjunction with the defrost timer. If the defrost timer should stick during defrost the bimetal will terminate the heater.