Abstract: The specification discloses a novel refrigeration/air exchanger unit (30) adapted for use with a main refrigeration unit (28) of a trailer truck (10) including frozen and refrigerated compartments (20, 22) to maintain the refrigerated compartment at a predetermined temperature above freezing without an auxiliary refrigeration unit. The system (30) includes a duct (34) interconnecting the compartments, a fan (44) for drawing cold air from the freezer compartment into the refrigerated compartment to lower the temperature therein, and another fan (62) and associated heating element (72) in the refrigerated compartment for modulating the temperature therein. The fans (44, 56) and heating element (72) are automatically controlled responsive to circuitry including a thermostat (78).