CLEAN & CHECK ON 30YR HEATING SYSTEM. CHECK ALL ELECTRICAL CONNECTIONS. CHECK MANIFOLD GAS PRESSURE AND FOR PROPER VENTING. CLEAN AND CHECK BURNERS AND BURNER OPERATION. ADJUST BLOWER COMPONENTS, AND LUBRICATE ALL NECESSARY MOVING PARTS. CHECK THERMOSTAT, AIR FILTER, AIRFLOW, HUMIDIFIER, HEAT EXCHANGER, HIGH LIMIT CONTROL, HUMIDIFIER, AND ENERGY CONSUMPTION, SHOWING NO ISSUES.