Performed comprehensive tune-up on 5-year-old Carrier furnace. Addressed homeowner's CO alarm concerns by identifying expired detector with low battery. Inspected furnace components finding strong igniter, cleaned and restored flame sensor, confirmed good condition of draft motor, blower motor, and heat exchanger. Combustion analysis verified safe and efficient system operation. Explained heat pump operation relative to outdoor temperature sensor and balance point settings. Customer enrolled in family rewards program.