On arrival system running and cooling producing 23 degree delta. This triggered deeper refridgerant diagnostic. Found a subcool of 3 when the typical range on a Goodman is 6-8. Found no leaks at condenser. Large quantities of dust have accumulated on blower due to dust bypassing filter. Current uv system is unable to prevent bacterial growth from spreading via airflow. Recommended adding iaq 200 uvc system that cleans surfaces and airflow and an April aire filter to prevent dust bypass. Further recommended speaking with a comfort advisor about system replacement due to age and low refridgerant. Customer declined all recommendations at this time but would like to discuss air quality further in the future.