What I cannot believe is this post started on Monday, it is now wednesday, and there are no answers from a visit from a Service Tech yet? Can't be that cold in N. E. if it is and your buddy is still fighting this without an experienced eye having inspected it, I hope he continues to be able to wake up in the morning! Tell him to get a tech there 1st thing tomorrow(or is there only 1 tech in the 100 mile radius)
Have the Tech check the vent tube and the vent chamber for any rust blockage or bits of broken rust particles also have him check the flue vent for any small obstruction. Those issues do cause systems to operate erratic or not at all from time to time, a lot of this in Houston TX on Trane's, Goodmans and Lennox gas fired furnaces.