Furnace tune up, cleaned flame sensor, CO test in flue and airstream. Normal levels of CO and XS air found in exhaust. No CO found in airstream. Checked pressure switch and high limit sensor. Cleaned furnace compartment. Checked 90% drain hoses and removed debris that was causing a partial blockage of hose. Checked wiring and board. Replaced filter. Removed, cleaned and wire brushed burner assembly. Found ventor motor bearings to be noisy and worn, average life expectancy for this unit is 14 years due age and condition of this unit failure is expected. Job complete.