Performed comprehensive tune-up on 19-year-old Goodman furnace. Diagnostic testing included combustion analysis via Testo 310 and electrical measurements with Fluke 116 multimeter, confirming proper function of igniter, flame sensor, gas valve, control board, draft motor, and heat exchanger integrity. Replaced blower capacitor which tested below manufacturer specifications. Noted early signs of potential future heat exchanger deterioration that should be monitored.