Performed prepaid maintenance on three train heat pump split systems .Amp drawâ€™s, refrigerant pressures, airflow, and motors are ok . Cleared the drains .found several issues with the main floor unit or the downstairs unit. The evaporator coil is heavily corroded ,this is at fail point in my opinion. The filter dryer on the outdoor unit is corroding heavily as well. Air quality coming out of the downstairs unit is not as good as it could be due to moisture inside of the unit. Recommending blue tube ultraviolet system to deal with any microbial growth . In all reality the downstairs unit should be replaced due to several major repairs that will need to be done soon . If you would like to speak to a comfort adviser about replacement on this downstairs unit, please call the office . For the two newer units no further action is needed at this time.