If its over 5 years,it's probably the ignition control.Should be a square box with some wires attatched to it,1 maybe 2 screws holding it on.Easy to replace.as long as you keep track of where each wire goes.Rheem has a ok Q&A line to call,just got to get a person on the line.May need to get part from them anyway.Rheem parts here are hard to get for powervents,may be better where you live
