My heating unit blower will not come on in the (Fan Auto Mode). I hear the
Heater come on but after a few seconds it shuts off. I assume there is some
Type of limiter that shuts it off due to the blower not turning. The blower
Will work in the (Fan On Mode) so this tells me the blower is working
Properly. What is preventing the blower from not working properly in
The (Fan Auto Mode)?

There is a item on most furnaces caller a fan limit control or a fan control. It is possible that the control is defective. Look at the sticky notes at the beginning of this board.