Former blue shield plan member, Fall tune up. Homeowner wants to sign back up on Blue Shield plan today. Talked about thermostat and filter operation. Showed customer how to access filter inside furnace at the base. Furnace is an upflow system. Remove removed washable allergy, pro 2000 filter and cleaned it thoroughly and left it out in the sun to dry. Checked drain line, evaporator coil, blower, heat, exchanger, burner, crossovers, connections, and hoses. Clean flame sensor. Replaced allergy pro washable filter. Cycled system on. Checked order of operation, measured heat rise and temperature split. Checked gas pressure, motor amps, carbon monoxide levels. System working great at this time.