Performed the level 2 furnace cleaning. Burners and flame sensor are clean. Heat exchanger looks good. Combustion readings were normal. No CO detected in the air. Drain is clear. Heat rise was 47°. The transition assembly has a small crack in it. I recommended replacing before the crack gets bigger and causes water damage. Average life of system is 12-15 years. Furnace is currently 16 years of age. Future life expectancy cannot be determined. Unit is heating properly at this time.