Came out to perform preventative maintenance on furnace. Inspected and changed filters for customer. Inspected the blower assembly, motor, electrical components, burners, flame sensor, ignitor, gas valve, pressure switch, safeties and overall condition of equipment in closet area. Asked customer how new ac did for him this summer and he stated that it worked well. Customer did ask to have next service done later in may so a better check of refrigerant pressures can be done. Told him that I would note it to be done in late may. I cleaned the flame sensor and brushed dust off the burners and components. Checked thermostat operation, wiring, amps, temperatures and gas pressure. Made sure furnace cycled fully before putting it back back together. Furnace is heating properly within manufacturing specs at this time.