Furnace clean and tune. Cycled system. Checked heat exchanger, found two chambers with cracks forming. Checked, removed and cleaned burners and flame sensor. Found igniter/flame rod assembly is worn and needing to be replaced. Ventor motor bearings are worn and in need to replacement. Checked and tighten electrical connections and clamps. Cleared drain lines. Preformed combustion test and found elevated levels of XS air in the exhaust. This is an indication of clogged secondary heat exchanger. Also found that system was going off on high limit safety. This is confirmation of blockage. Average life expectancy for this unit is 14 years, this system is well over that time and in very poor condition. Second opinion set for today for options. No charges pending results of second opinion. Job complete.