Keystone air conditioner emits a musty or moldy odor when it starts.

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

Steps:

• Clean filter: Wash the filter thoroughly with soap and water and let it dry.
• Clean evaporator: Remove the front cover and spray a foaming coil cleaner approved for air conditioners onto the evaporator fins. Allow it to work and drain per product instructions.
• Disinfect drain pan: Wipe the condensate pan with a mild bleach solution (if compatible with materials) or a coil-safe disinfectant to kill mold.
• Run fan-only mode: After cleaning, run the fan-only mode for 30–60 minutes to help dry the coil and pan.
• Regular maintenance: Repeat cleaning at the start and end of each cooling season to prevent recurrence.