CLEAN AND CHECK HEATING UNIT ON A 9 YR UNIT. CHECK THERMOSTAT, AIR FILTER, HEAT EXCHANGER, HIGH LIMIT CONTROL, AIRFLOW, HUMIDIFIER, ENERGY CONSUMPTION, GAS PRESSURE, AND ALL ELECTRICAL CONNECTIONS. CLEAN AND CHECK BURNERS AND BURNER OPERATION. LUBRICATE ALL NECESSARY MOVING PARTS, AND ADJUST BLOWER COMPONENTS