To access the evaporator coils, remove the coil access panel. To remove the access panel, remove the metal tape that seals the panel.
Next, take out the screws on the access panel of the evaporator coil to the air handler. Use mild soap and warm water to clean the coils.
Get a spray bottle and put hot water and cleanser in it. Apply detergent liquid to the evaporator coils. Allow the mix to soak in and break the debris.
When this is done, wipe off any loose dirt and material with a towel or brush.