Abstract: An evaporative precooling unit for use with a conventional refrigerant type air-conditioning system having an exteriorly mounted compressor housing including a compressor, a condenser, a side air inlet, a top air outlet and a fan for directing air through the side air inlet and out the top air outlet to cool the compressor and condenser, includes a precooler housing dimensioned to be installed over the side air inlet of the compressor housing. The precooler housing may utilize either water saturated pads or spray nozzles to provide evaporative cooling to the air entering the compressor housing. In an alternative embodiment, a precooler housing having a bottom cooled air outlet dimensioned for registry with the top air outlet of the compressor housing is utilized to supply cooled air to the compressor and condenser upon reversal of the compressor cooling fan blades.