I have a newer forced air gas furnace (5 or 6 yrs old) with a 2-speed fan. After connecting the wires as instructed from the online video and instructions during the setup, I am only getting the high speed on the fan running when the heat kicks in. I would like to get the lower speed to run also. When I connected the wires at the furnace, I noticed a second set of wires connected to the board at the Y and the C terminals. I assume that is what is controlling the 2 speeds.
you need to show a picture of your wiring. usually the fan speed is controlled by the furnace board, but you might have miswired something.