When i am finished with the heat from my pellet stove I normally push the Red switch down to shut down the augar which feeds the pellets. Normally the fan runs until the temperature has sufficiently decreased prior to shutting off, but now as I push the red switch down the fan stops immediately before the coals have cooled down to a safe temperature. Which part should I look at to replace so that the stove properly cools down prior to shutting off?