Performed the level 2 furnace cleaning. Burners and flame sensor had a lot of oxidation to clean off. Igniter ohmed a little high. Heat exchanger has a lot of rust, however, no cracks located at this time. Combustion readings were normal. No CO detected in the air. Drain is clear. High limit passed the safety check. Heat rise was 53Â°. Unit is heating properly at this time. Due to age and condition, I recommended keeping an open mind for options in the future. Life expectancy cannot be guaranteed.