Abstract: Improved means for automatically controlling an evaporative cooler having a pump and blower, said control system comprising a solid state electronic temperature sensing circuit capable of sensing temperature differences of considerably less than 0.1 degree Fahrenheit, a timer for activating the cooler pump a predetermined period prior to and following activation of the blower, logic means for controlling activation and cycling of said blower, and humidity sensing means for developing an electrical signal indicative of excessive atmospheric humidity for turning off said cooler and controlling an associated air conditioner.