Bill, Do you have thesame thermostat on both furnace? The LED blinking indicates the the electronics module locked-out due to sensor failed to detect heat at the chamber. Or the sensor detect over heat due to the blower motor fail to run after the fourth tries. When you turn-off main power switch, you reset the module the the senosr will detect the heat and the blower motor this time will turn-on. I think this model have bad electronic module design. Lennox should have replace electronic module free of charge.