Performed preventative maintenance for gas furnace. Inspected all the electrical components. Confirmed proper high and low voltages. Customer replaces the standard air filter 16x25x1. Cleaned the burners, flame sensor and burner compartment. Performed a combustion analysis on the furnace. System is operating at 83% efficiency with a CO level of 17ppm. System had a temperature rise of 49° with the outdoor temperature at 77°. System is operating properly at this time. Found no sign of dye inside near the coil. Will need to inspect the condenser early spring to find where the refrigerant leak is coming from to repair it. Customer would like to take care of his own humidifier. The #35 water panel will be replaced by him once every season. Model #Tg8s100b12mp11 Serial #W1c8657380