Performed annual 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 blower wheel beginning to get dirty. Recommend a cleaning to increase airflow and efficiency of system and to avoid any issues with overheating system. Main flame safety fluctuates with stages of furnace. Starts up in range in high fire, drops below in low fire, then rises again as furnace ramps up. Flame saftey is testing out well at this time.