Turn off power to the AC unit at the thermostat and breaker
Remove the access panel to reach the indoor evaporator coil
Inspect the coil for dust, dirt, and mold
Vacuum loose debris with a soft brush attachment
Apply a no-rinse evaporator coil cleaner
Let the cleaner sit for the recommended time
Gently wipe accessible coil surfaces with a soft cloth or brush
Clean the drain pan and clear the condensate drain line
Replace the access panel
Restore power and run the system to check operation
Schedule professional cleaning if the coil is heavily dirty or hard to access