Indoor unit emits a musty, moldy, or sour smell when operating

Safety first: Turn off power before cleaning. Use only non-corrosive coil cleaners approved for aluminum fins.

Steps to improve:

• 1. Clean filters: Wash filters thoroughly with mild detergent and dry completely.
• 2. Clean evaporator coil: Use a foaming no-rinse coil cleaner sprayed onto the coil surface. Allow it to work and drain into the pan.
• 3. Clean drain pan: If accessible, wipe the drain pan with a cloth and a mild disinfectant solution to remove slime and mold.
• 4. Run in FAN mode: After cooling, run the unit in FAN-only mode for 30 minutes to dry the coil and reduce odor buildup.

When to call a technician: For severe odor or visible mold deep inside the unit, professional disassembly and chemical cleaning may be required.