2ND 13 POINT MAINTENANCE CHECK-UP FOR 6YR HEATING UNIT. LUBRICATE ALL NECESSARY MOVING PARTS AND ADJUST BLOWER COMPONENTS. CLEAN AND CHECK BURNERS AND BURNER. CHECK MANIFOLD GAS PRESSURE AND FOR PROPER VENTING. CHECK THERMOSTAT, AIR FILTER, AIRFLOW, FAN CONTROL, HUMIDIFIER, AND ALL ELECTRICAL CONNECTIONS. CHECK HEAT EXCHANGER AND HIGH LIMIT CONTROL.