CLEAN AND CHECK HT. CHECK THERMOSTAT, CHECK BURNERS AND BURNER OPERATION, CHECK HUMIDIFIER, CHECK ALL ELECTRICAL CONNECTIONS, CHECK HEAT EXCHANGER, CHECK HIGH LIMIT CONTROL, CHECK AIR FILTER, CHECK GAS PRESSURE AND FOR PROPER VENTING, ADJUST BLOWER COMPONENTS, LUBRICATE ALL NECSSARY MOVING PARTS. EVERYTHING IS RUNNING GREAT.