Performed seasonal precision tune up on heating systems; cleaned burners, tested ignition components, adjusted gas levels, tested safety circuits, checked indoor motors, checked all electrical components, tested indoor air flow, checked heating temperatures, and tested overall furnace operations. Air Exchanger cleaning and tune up. Remove filters and core to vacuum. Also clean cabinet interior. Inspect bearings on blower assembly. Install core and filters. Clean off outside hoods. Test operation of air exchanger. Replaced flame sensor under warranty. Will clean blower wheel and install surge protector on a later date. Recommend an electronic air filter, duct cleaning, and an air purifier.