The basic maintenance routine for an evaporative air cooler is to perform a visual inspection of the unit every six months. During this time, you should check for any potential obstructions in the water flow that could cause damage to the machine. You should also check the water level, filter, and evaporative pad. If there is any sign of damage or wear on these components, it is recommended that you have them replaced. Other routine maintenance tasks include checking the evaporative pad for clumps or tears and cleaning the water evaporation system with a mild detergent.