Came out to perform preventative maintenance on furnace. Discussed with customer about maintenance needed and any issues she may have. Customer stated her filters needed to be changed and that the heat has been running fine. Changed customer supplied filters. Did a thorough inspection of the blower assembly, electrical components, heat exchanger, burners, flame sensor, hsi, gas valve, ducting and overall condition of equipment in attic. Cleaned flame sensor and brushed dust off the components. Checked thermostat operation, wiring, capacitor, amps, temperature rise and gas pressure of furnace. Tested pressure and safety switches. System overall is good condition and is heating properly within manufactured specifications.