Came out to perform preventative maintenance on furnace. Discussed with customer about maintenance being provided, filters and any issues. Inspected and changed filters for customer. Inspected the blower assembly, motor, electrical components, burners, flame sensor, ignitor, gas valve, pressure switch, safeties and overall condition of equipment in closet area. I cleaned the flame sensor and brushed dust off the burners and components. Checked thermostat operation, wiring, amps, temperatures and gas pressure. Made sure furnace cycled fully before putting it back back together. Furnace is heating properly within manufacturing specs at this time.