A mechanism for controlling the temperature in and the flow of air between freezer and fresh food compartments in a refrigerator is constituted by a pre-assembled control unit including a housing within which is mounted fresh food and freezer compartment control knobs, a thermostatic controller, a temperature sensing capillary tube, a defrost timer, an automatic damper unit for adjusting the opening of an air passageway formed in the housing, and lighting assemblies. The air passageway formed in the housing is adapted to be aligned with an opening leading from the freezer compartment to the fresh food compartment. The capillary tube has one end attached to the thermostatic controller and another end positioned in the air passageway such that the thermostatic controller receives temperature signals from the capillary tube that are associated with not only the temperature of the freezer compartment, but also the temperature of the fresh food compartment. The capillary tube is maintained in the desired position within the air passageway by means of a tube holder. The end of the capillary tube is preferably covered by a sleeve for thermal damping purposes. Since the control mechanism is pre-assembled, only a few mechanical connections are required to secure the entire control mechanism within the refrigerator.