Did a maintenance on a Coleman gas furnace. During the maintenance I clean the flame sensor. Also poured water down the drain to make sure the drain was working. Change the 16 x 25 x 1 filter. Did a combustion test the oxygen level was 19 and the CO level was 9. Supply air temp was 127 degrees. Also did a amp prereading on the inducer motor and the blower motor which are both in range of the furnace specs. Also cleaned out the burner rack and the blower motor housing. System is operating properly at this time. M# Tg9s080b12mp11b s#W1m8350719.