Heat Tune Up for 140KBTU natural gas furnace. Inspection of heat exchanger, burners and ignitor: Good. Cleaned flame sensor; verified flame sense/rectification circuit. Replaced 16x25x1 filter. Checked gas pressure. Checked all controls, wiring, electric motors and components. Verified thermostat operation. Measured temperature rise and static pressure. Combustion/draft test: Good Homeowner renewed plan membership. Furnace is operating well at the time of this maintenance.