A solid-state control for a variable air volume (VAV) temperature conditioning system adapted to control a plurality of refrigerant cooling stages, and in particular, to modulate an outdoor air economizer. The control includes both an outdoor ambient air and a discharge air temperature sensor. Further included are means for selectively modulating the economizer either in response to the deviation of the discharge air temperature from a setpoint or in response to the discharge air temperature, depending upon the relative magnitudes of the outdoor and discharge air temperature, and upon one or more stages of cooling being energized.