BMW Repair: 99 328i pusher fan stays on always, free wheels, driven fan

Question
On our 99 328i the a/c electric pusher fan (in front of the radiator) stays on even
after you shut off the car and remove the key. It just started today. Please help.

Answer
Hi Hector,
It is normal for the auxillary fan to run for a number of seconds after key off (remember that it free-wheels and will not stop readily like a belt driven fan).
But if it really whirls as if it is still powered by current after key off,particularly when the engine is not overheating,
then there is something really wrong.
The fan is always supplied B Plus by the battery. It has a built-in final stage (resistor/switch) within the motor housing itself. The signal to run is provided by the DME (engine computer) thru a grounding signal.
Since the DME is turned off when the key is off, then it is logical to assume that the built-in final stage is switching the motor on its own. Or the grounding signal is shorted to ground already. Look at the upper right side of the radiator  and you would see a box-like connector set that has wires leading into the electric fan. If the wires seems OK, then
the fan motor itself is defective.
Tino