Performed heating maintenance on one heat pump system. Checked all electrical, mechanical and performance of the system. I ran the system in cooling mode to check refrigerant levels because the outdoor temperature is 65°. Refrigerant levels were slightly low, and I also found small amounts of microbial growth on the blower wheel. I informed the customer and presented options for repair. She declined repairs at this time and wants to see how the system looks on her next maintenance visit. No other major issues were found, and the system is operational at this time. See attached checklist for full tune-up details.