Furnace heating tune-up and safety inspection. Cleaned and serviced furnace. Customer renewed VIP maintenance plan. Tested all mechanical components. Cleaned all sensors. Tested gas valve voltage and inlet/outlet pressures. Tested blower motor amperage. Changed the furnace filter that the customer provided. Found HSI and Fs very corroded, and the customer agreed to replace both parts. Changed thermostat batteries. The system is clean, heating, and operating properly at this time. Performed free PLUMBING inspections.