Evaporative coolers are used in hot, dry climates for energy efficient cooling. They blow air through water-soaked pads that cools the incoming air as much as 30 degrees, depending on the humidity. When the humidity rises, the evaporation coolers are less effective, since the extra water in the air hinders the evaporation process. Mechanically, evaporative coolers are far simpler to troubleshoot, service and repair than air conditioners, so many people who have them learn to maintain and repair the coolers themselves.
Check the Belt and Motor
Check the motor if there is no airflow. The switch might have accidentally been turned off. If the switch is on and the motor will not run, make sure that the motor is plugged in.
Test the outlet that the motor is plugged into. If the switch is on and the motor is plugged in, see if the outlet is delivering power by plugging in a lamp or a hair dryer from the house. If the outlet is the culprit, replace it if you feel comfortable working with electricity. If not, call an electrician. Make sure you disconnect the power to the cooler before working on the outlet.
Look at the belt if the motor is running and there is no airflow. The belt may be broken or is slipping on the pulleys. Check the belt for tears, rips, or dry rot. Replace the belt if it has broken or is worn.
If the belt is slipping, adjust the motor to tighten the belt. Use the adjustable wrench and screwdriver to move the motor up to tighten the belt. If it is difficult to turn, use lubricating spray to loosen the nut or screw. The insides of evaporative coolers are humid and rust is not uncommon on the metal parts.
Check the Pads and Water Pump
Feel the pads for moisture. If they are dry, there could be a malfunction in the water pump or the spiders that deliver the water to the top of the pads. A hose goes from the pump to the spider on top. The spider delivers water to the pads. Take the hose off and see if water is being pumped. Point the water outlet on the pump away from you as you do this to stay dry.
Replace the pump if it is not working. These are available at home improvement stores, many plumbing supply stores, or heating and air conditioning shops that stock parts for evaporative coolers. Make sure that you unplug the power to the cooler before removing the old pump and installing the new one.
Check the spider at the top of the evaporative cooler if the pump is working to see if there is a blockage or a disconnected pipe that is not allowing enough water or any at all to flow to the pads. If the pipes are connected properly, remove the spider by loosening the bolt on top of the cooler that holds the spider in place. Try to loosen the blockage with a stiff wire or canned air. If the block is serious, replace the spider.
Look for calcium deposits on the pads if the pump and spider are operational. Arid regions where evaporative cooling is effective often have hard water that builds up on the pads as the water on them evaporates. Replace the pads if the calcification on them is reducing both air and water flow.