You are correct. It has a fan and limit. The fan is heat sensitive action making contact on rise and open on drop. The switch can lose calibration over time. In electric mode the fan is brought on automatically without the presense of heat.
See page 13 here -
There is very little wiring on this unit. The conduit will bring power into the unit. Then a conduit will go to a rectangle box located at the top of the furnace.....this is the blower/limit control.
Sticking out the back of the switch...