Evaporative air conditioners are basically air blowing across a pad that gets flushed with water. These large pads that sit in the box on the roof simply soak up the water so the air can blow through them. They basically look like large bails of hay.
Like all equipment however, over time these pads will become clogged with insects, mineral deposits and become brittle due to exposure to the elements. These evaporative air conditioning pads can be easily changed over by an commercial air conditioning repair company. But if you want to save a bit of money and do it yourself that’s pretty easy too.