This is an intermittent problem that is fixed by disconnecting power to the unit and allowing control board to reset.

The draft fan comes on and runs normally, the ignitor coil comes on and glows, a clicking sound comes from the circuit board (the automatic ignition system relay seems to be the culprit), then the furnace tries to ignite as a flame flares for less than a second and the clicking stops, and the ignitor coil stops glowing. Then the sequence starts over again.

When I disconnect power everything works perfectly. The only difference that I can discern is that there is no longer a clicking sound from the automatic ignition system relay on the control board.

Here is a video showing the sequence.

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