SECOND MAINTENANCE CHECK-UP FOR 12YR HEATING SYSTEM. CLEAN AND CHECK BURNERS AND BURNER OPERATION. ADJUST BLOWER COMPONENTS, AND LUBRICATE ALL NECESSARY MOVING PARTS. CHECK THERMOSTAT, AIR FILTER, AIRFLOW, FAN CONTROL, HUMIDIFIER, HEAT EXCHANGER, HIGH LIMIT CONTROL, AND ALL ELECTRICAL CONNECTIONS. CHECK GAS PRESSURE AND FOR PROPER VENTING.