Performed preventative maintenance for horizontal gas furnace. Cleaned out the burners and flame sensor. Inspected all the electrical components. Tested the amp draw from the blower and inducer motors. All are operating within manufacturer spec. Customer has ordered the Merv 16 air filter (20x25x5) themselves. Performed a combustion analysis on furnace. System is operating at 83% efficiency with a CO level of 11ppm. Confirmed proper high and low voltages. Cleaned out the inducer port that is known for buildup debris over time. System is operating properly at this time. Model #SL280UH090V60C-04 Serial #5915J04723