Did they preventative maintenance on a gas furnace. During the maintenance I clean the flame sensor And cleaned out the burner box and the blower motor housing. Did a combustion test and the ppm was 30 and the O2 what is 8.8. Changed out the 16 x 25 x 1 filter. It’s an amp check on the inducer motor and blower motor which both met the furnace specs. Customer stayed at one day last week he had to go downstairs and check on the heater because the blower motor was making a very loud noise. Arriving today I did not hear no loud noise and the amperage on the blower motor is in range. System is operating properly at this point M#EL280UH110P60C-01 s#5912F32483