Turn off power to the HVAC system
Remove the access panel to reach the evaporator coil
Inspect the coil for dust, dirt, and mold
Use a soft brush or vacuum with a brush attachment to remove loose debris
Apply a no-rinse evaporator coil cleaner
Let the cleaner sit for the recommended time
Wipe away loosened dirt with a soft cloth if needed
Clean the condensate drain pan and drain line
Reinstall the access panel
Restore power to the system
Replace the air filter
Schedule professional cleaning if the coil is heavily soiled or difficult to access