Performed preventative maintenance on furnace for customer. Changed the filter for customer. Inspected blower assembly, motor, capacitor, heat exchanger, burners, flame sensor, igniter, inducer motor and overall condition of equipment. Cleaned the flame sensor and dust off the burners and components. Checked thermostat operation, wiring, amps, temperatures and gas pressure. System is heating properly within manufacturing specifications at this time, but I did recommend customer start planning for replacement due to age and parts starting to wear down internally.