My house has a BDP furnace, model number 394gaw048100 and the fn or blower run constantly. I know the wires from the circuit board to the thermastat are not shorted because when I disconnected the white, red, green, yellow wire from the circuit board, the blower still runs. The circuit board has the clear relays solder on and it appears that the relays are good but since they are soldered on the board, I can replace it to find out if that the issue. Could it be something on the circuit board that went bad and the circuit board needs to be replaced? Are there other things that could be causing this? I heard that a blown fuse can cause this issue, but I can not find any fuses, any help is appericated.

It could be the circuit board OR there is usually a limit control for the heat section of the furnace that when tripped it will cause the blower to run all the time as a safety to remove the heat. Look on the back of the furnace blower door for a wiring diagram.