I have a RGU80 gas furnace that cycles through the normal routine three times and then the watchdog initiates. Routine is combustion motor comes on, few seconds later the flame ignites (which means pressure switch is good) and after another few seconds the flame extinguises. It does this three times and then the LEDs alternate flashing.

Any clues as to what the problem may be? Main blower? Starting capacitor? Or am I totally off track?