Turn off power to the AC unit at the thermostat and breaker
Remove the access panel to reach the indoor evaporator coil
Put on gloves and a mask
Vacuum loose dust and debris from the coil area with a soft brush attachment
Spray the coil with a no-rinse evaporator coil cleaner
Let the cleaner sit for the time listed on the product label
Gently wipe accessible coil surfaces with a soft cloth or brush
Clean the condensate drain pan and drain line if accessible
Reinstall the access panel
Restore power to the unit
Replace the air filter if dirty
Schedule professional service if the coils are heavily clogged or damaged