A swamp cooler is used in dry climates to cool a home or other building. Swamp coolers are also known as evaporative coolers, since they rely on the evaporation of water to cool the air. When water evaporates, the air temperature drops. This cooled air is pulled through the house and blown outside through open windows or ceiling ducts. Swamp coolers cost considerably less to run than air conditioners. They are easy to troubleshoot when not working properly, unlike air conditioners or heat pumps.
Check the power supply if the unit is not running at all. Window swamp coolers plug into wall outlets. Roof units plug into weatherproof outlets on the roof. If the pump is not working, the outlet may be bad. Try plugging in a hair dryer or other small appliance to check the outlet. If the outlet is bad, check the circuit breaker. If that hasn't tripped, the outlet is likely defective and must be replaced.
Disconnect the unit's pump if the outlet is working properly--the pump and motor may need to be replaced. Unplug the water hose and the plug to disconnect the pump from the swamp cooler. Test the pump in another outlet to verify that it doesn't work. Double-check the motor by turning the power back on to the swamp cooler and pushing the "on" switch. If the motor doesn't run, it must be replaced.
Inspect the belt if the evaporative cooler is not blowing any air, but the motor is running. The belt runs off the motor to turn the unit's fan or squirrel cage. Belts can break, causing the cooler to stop blowing air. Replace old, frayed belts.
Examine the condition of the pads while inspecting the belt. Clean or replace the pads if they have a lot of mineral deposits. Encrusted pads do not absorb water well and they block the air flow, cutting down on the cooler's effectiveness.
Push the float down, with the water on, to see if it's functioning. When the float is depressed, a little water should trickle into the cooler. If the float does not release water, make sure the faucet and water are on and that the line to the cooler is not blocked. Replace the float if the lines are clear.
Check the dew point, temperature and humidity. When the dew point goes over 55 F, evaporative coolers stop working as effectively. If the components are all working but the house is hot, high temperatures and humidity may be reducing the unit's cooling power. Unfortunately, only drier air and cooler temperatures can help cool the house when the humidity rises.