Performed single system heating maintenance. Serviced condensate drain line. Inspected electrical connections, and components of gas furnace. Removed cleaned and reinstalled flame sensor. Cleaned up roofing debris from around furnace and flu piping. Replaced 16 x 25 x 1 filter. There is still a new filter there for customer. Inspected the outdoor unit electrical wiring and components. At this time the system is operating properly.