Faulty FSU (Final Stage Unit)

[BMW_E53]

Hey guys I have a problem with my front ventilation fans and I am suspecting it is because of a faulty FSU. What happens is no matter what fan speed I set, the fan would either not run at all or it will stay in its own set speed. Also it won't run at all and then out of nowhere it blows at a high speed for a couple of seconds and then shuts off. What really set my suspicion was yesterday night when the car was off no key in the ignition and the blower was still running. And no I did not set the auxiliary ventilation! The blower motor literally had a mind of its own! So before I buy the FSU part, I would like to ask you guys if you had a similar situation like this before, and did replacing the part fix this problem? Thanks!