CLEAN AND CHECK HT. CHECK THERMOSTAT, CHECK BURNERS AND BURNER OPERATION, CHECK HUMIDIFIER, CHECK HEAT EXCHANGER, CHECK GAS PRESSURE AND FOR PROPER VENTING, CHECK HIGH LIMIT CONTROL, CHECK FAN CONTROL. ALSO, CHECK CONDENSER COIL, CHECK FREON LEVELS, CHECK AIR FILTER. ADJUST BLOWER COMPONENTS, LUBRICATE ALL NECESSARY MOVING PARTS. EVERYTHING IS RUNNING GREAT.