Came out to perform preventative maintenance on furnace. Changed out customer supplied filters. Discussed filtration and better options for customer and ways to help keep his existing filters in place. Inspected the blower assembly, motors, electrical components, burners, flame sensor, ignitor, gas valve, pressure switches, safeties and overall condition of equipment in closet. Cleaned flame sensor and dust off the burners and components. Checked thermostat operation, wiring, amps, temperatures and gas pressure. System is heating properly within manufacturing specs. Customer had no other questions or concerns at this time. Thank you for choosing Interstate. Happy Holidays! - Isaac