Musty or moldy smell from the air conditioner when it starts or runs.

Safety: Unplug the unit. Wear gloves and a mask if you are sensitive to mold.

Steps:

• Clean or replace filter: Wash the filter thoroughly or replace it if heavily soiled.
• Clean evaporator coil: Remove front cover and apply a foaming coil cleaner designed for AC units. Allow it to work and drain as directed.
• Clean drain pan: Wipe the condensate pan with a mild bleach solution (1 part bleach to 10 parts water) to kill mold. Rinse and dry.
• Clean blower wheel: If accessible, brush and vacuum dust and growth from the blower wheel.
• Run in FAN mode: After cleaning, run the unit in FAN-only mode for 30–60 minutes to help dry internal components.

Note: Persistent severe odors may require professional deep cleaning.