Brushed and vacuumed flue pipe and heat exchanger Replaced oil filter, nozzle, and strainer Checked all electrical connections and safeties Performed combustion and smoke tests 7.8%o2 48ppm co 0 smoke When arriving unit was off on reset. Pushed reset button and furnace lit right away. Checked oil flow and had good flow. Checked the igniter and saw the spark was an orange/yellow color indicating it is getting weak. After getting customer authorization we replaced the igniter. Started and tested unit. Unit is working properly.