Performed the level 2 furnace cleaning. Burners and flame sensor are clean. Heat exchanger is rusting and chipping but no cracks located at this time. Combustion readings were normal. No CO detected in the air. Drain is clear. Heat rise was 47°. The flame sensor is warped and needs to be replaced. Part is covered under the parts warranty. We will return with the flame sensor later. Unit is heating properly at this time.