MAINTENANCE CHECK-UP FOR AN 8 YEARS OLD HEATING UNIT. BURNERS WERE A LITTLER RUSTY. CLEAN AND CHECK BURNERS AND BURNER OPERATION. ADJUST BLOWER COMPONENTS, AND LUBRICATE ALL NECESSARY MOVING PARTS. CHECK GAS PRESSURE AND FOR PROPER VENTING. CHECK THERMOSTAT, AIR FILTER, HUMIDIFIER, HEAT EXCHANGER, HIGH LIMIT CONTROL, AND ALL ELECTRICAL CONNECTIONS.