Indoor unit produces a musty or moldy odor when cooling starts

Safety first: Turn off power to the indoor unit. Wear gloves and a mask when cleaning moldy components.

Steps:

• 1. Inspect coil and pan: Remove the evaporator access panel and look for visible mold or slime on the coil and in the drain pan.
• 2. Clean coil surface: Use a non-acidic foaming coil cleaner approved for indoor use. Follow label directions and avoid overspray on electronics.
• 3. Clean drain pan: Wipe out sludge and debris. Flush the pan and drain line with a mixture of water and a small amount of bleach or coil cleaner (avoid strong bleach on metals).
• 4. Replace filter: Install a new, quality filter to reduce organic buildup.
• 5. Control humidity: Use dehumidification features or a standalone dehumidifier to keep indoor RH below ~55%.