Furnace precision tune up; clean and tune up furnace; clean burners, test ignition components, adjust gas level, test safety circuit, check indoor motors, checked all electrical components, tested indoor air flow, checked heating temperatures, and tested overall furnace operation. Found the main ignition system testing out of range this could impact the operation of the furnace, also found the main flame safety device testing out of range this will also impact the operation of the furnace. Lastly I visually checked the heat exchanger for any cracks or fractures and couldn’t find any at this time but found major rust, this rust could lead towards failure on the heat exchanger. Lastly with age of the furnace repairing would not be beneficial to the homeowner and replacement would be encouraged. All recommendations declined at this time.