CLEAN AND CHECK HEATING UNIT. CHECK ALL ELECTRICAL CONNECTIONS. CHECK THERMOSTAT, AIR FILTER, AIRFLOW, HUMIDIFIER, FAN CONTROL, AND CHECK MANIFOLD GAS PRESSURE AND FOR PROPER VENTING. CLEAN BURNERS AND CHECK BURNER OPERATION. LUBRICATE ALL NECESSARY MOVING PARTS. CHECK HEAT EXCHANGER AND HIGH LIMIT CONTROL. FIXED GAS COCK.