Harman Stove Company Accentra Service Training page 44

Feeder Position Switch
Used on the Invincible Series, and older P-61's. Ensures that the
slide plate is closing when the pusher arm returns. If the switch
doesn't sense a full closure for a period of 30 minutes, it will cause
the status light to blink "2 blinks". During this period, if the unit is
turned to "off", it will not shut down until it runs out of fuel and the
ESP probe cools naturally. This switch has been eliminated on all
current models.
Harman Pellet Service Training 44