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Rheem furnace cycles off after 2 seconds of flame
I have a Rheem furnace model RGED-09ERAJS 90,000 BTU drum type burner circuit board was a Honeywell it went bad so I installed a later model board M/N 1012-920A
purge blower run, pressure switch is made, hot surface ignition turns red hot, gas valve turns on and burner lights for 2 seconds then goes out and then it starts al over again I installed new hot surface igniter did not help (the hot surface igniter is the flame sensor has no flame probe or thermocouple ).The neutrals on circuit board are connected to the incoming power neutral wire and is connected to furnace. I also installed both new LPG regulators on gas supply to furnace, 10 inches of water column on burner manifold, cleaned burner orifice What am I missing?
HELP I need this furnace working