Brushed and vacuumed debris from heat exchanger, flue pipe, and burner tube. Checked all electrical connections and safeties. Sanded down flame sensor for a better flame sense. Performed a combustion test on unit, unit is running at 8.4% O2, with 30ppm CO. Recommend thinking about replacing boiler before next winter season due to age and condition of components inside boiler. Please call office to setup a quote when you are ready to replace unit.