A vapor compression refrigeration system (10) for cooling a cabinet (22) having a thermostat (19) for cycling the compressor (12) off and on to maintain a predetermined temperature range in the cabinet (22) includes a subcooling flow control valve (20) at the inlet to the capillary tube restriction (18). The valve (20) is operated by a sealed bellows (40) containing a refrigerant so that the valve (20) is responsive to the fluid entering the valve (20). The valve (20) is calibrated so that only a subcooled liquid refrigerant can flow through the valve (20) and if the entering refrigerant is above a predetermined level the valve (20) will close to completely block all flow between the condenser (14) and the evaporator (16), and the valve (20) will stay in the closed position at all times when the compressor (12) is not running.