CLEAN AND CHECK ON 18YR HEATING UNIT. CHECK HUMIDIFIER, THERMOSTAT, AIR FILTER, AIRFLOW, FAN CONTROL, ENERGY CONSUMPTION, HEAT EXCHANGER, HIGH LIMIT CONTROL. CLEAN AND CHECK BURNERS AND BURNER OPERATION. LUBRICATE ALL NECESSARY MOVING PARTS AND ADJUST BLOWER COMPONENTS. CLEAN AND CHECK MANIFOLD GAS PRESSURE AND FOR PROPER VENTING. LUBRICATE ALL NECESSARY MOVING PARTS AND ADJUST BLOWER COMPONENTS.