Arrived at the customer’s home to find the cause of a “mildew smell” coming from the vents when the system was switched to cooling, particularly on the main level. The customer found that the upstairs Apco-X had a fault and had a solid red LED. Found that the bulb for this upstairs UV light was broken and would trip a fault code after sparking. The UV lights both are high voltage model Apco-X Ultras which are more prone to faults than their low voltage counterparts. No issues were found with the main floor system at this time, it is possible that the main floor is pulling air from the upstairs and causing a stronger smell with a stronger blower motor. While fixing the issues with the upstairs system, both coils can be treated for odors using bacterial treatment chemicals. It is recommended to change the high voltage Apco-X Ultra for the upstairs to a low voltage Apco-X Ultra Dual model with a secondary UV light in the coil compartment. Reported results to the customer and scheduled to