Performed preventative maintenance on furnace. Customer will change filters. I supplied the filters to customer for her to change. I inspected the blower assembly, motor, capacitor, electrical components, wiring, burners, flame sensor, ignition, gas valve, inducer motor, and overall condition of equipment. Customer had an issue with the blower wheel previously and wanted it to be double checked. Blower motor amps are good, capacitor was replaced when we were out last and the wheel is still good. Blower assembly has a slight vibration, but nothing concerning. I checked amps, temperatures and gas pressure. Tested pressure and safety switches. System is heating properly within manufactured specifications at this time.