Hello. My furnace displays a 12 fault code. I've replaced the pressure switches, control board, flame sensor, and limit switch, I have a new capacitor and a new ignitor to swap out the respective components. The sequence: a call for heat will initiate the blower, in about 90 seconds the ignitor will glow and the firing sequence will begin. Of three burners, the first and second burner will ignite but the third fails and the sequence will start over for a total of three times and then the furnace will shut down. Subsequent calls for heat fail until I cut and restore power several times. Second issue that I'm having is that the furnace will not heat to the thermostat temperature setting. Any ideas or assistance is appreciated.