A musty odor that worsens when the AC runs can point to hidden mold in ducts or the evaporator

https://www.slideserve.com/katterobac/hvac-emergency-signs-that-point-to-a-serious-system-breakdown

A musty odor that worsens when the AC runs can point to hidden mold in ducts or the evaporator. Keep the filter fresh and arrange a thorough cleaning service.