Furnace clean and tune . Cycled system. Checked heat exchanger. Found all chambers with heavy rust and corrosion. No visible cracks found with camera. Checked, removed, and cleaned burners. All burners are rusted and damaged. Checked and cleaned flame rod/igniter. Igniter tested low and is very worn. Both the flame rod and the igniter are in need of replacement. Checked electrical connections and clamps. Tighter all. Cleared drain line. Found beatings are worn in Ventor motor. This is causing grinding and noise. This will cause motor to seize at any time. Preformed combustion test and found normal levels in exhaust. No CO found in airstream. Average life expectancy for this unit is 14 years. This system is 20 years old and in poor condition. System is operating safety at this time, but future failure is expected. Replaced ignition system and cleaned fireplace. Cycled system and fireplace operating normal at this time. Job complete.