open for a period exceeding a chosen maximum time the alarm is sounded as will be described later a monitor plug 50 through which a servicing data logger can be coupled to the unit 20 for diagnostic purposes is also provided as explained later reset circuitry 65 effects reset of the micro chip 20 when required to avoid upset and improper operation from random interference in known manner the various aspects of the operation of the new system will now be described under separate headings the directing of the air to the freezer compartment on the one hand and the food compartment on the other after it has been cooled by the evaporator in the frost free system has always been very approximate in most refrigerators the baffle is controlled manually by the user setting the baffle between a minimum and a maximum flow to the freezer compartment judged generally by the state of food in the freezer e g as by consistency of ice cream which hardens noticably at about 0 u00b0 f more accurate systems have employed some kind of cable control to the baffle operated by a temperature sensitive bellows which can be set by the owner to a preferred temperature the control effected is quite coarse and the system has a very slow response so that it cannot recover quickly from door openings heavy refrigerator loads or temperature rises produced in the defrost cycle the present arrangement allows.