Performed preventative maintenance on furnace for customer. Changed out filters for customer. Customer wanted system serviced due to the home being vacant for a few months and having a relative move into it. I Inspected the blower assembly, motor, capacitor, electrical components, burners, flame sensor, ignitor, gas valve, pressure switch, safeties and overall condition of equipment. Cleaned flame sensor and dust off the burners and components. Checked thermostat operation, wiring, amps, temperatures and gas pressure. System was showing no signs of any issues at this time. Customer is aware of systems age, and wants to keep it functioning properly as long as possible.