Whirring Noise At Shutdown

[JMI]

When the engine on my 1989 535i is shut off a whirring type noise is plainly audible coming from somewhere back behind the instrument cluster. Only lasts a few seconds. It sounds sorta-kinda normal, but I wouldn't know, this being my first BMW.
Any idea?

TIA

[Jay 535i]

It's the HVAC vents closing themselves. Normal.

[JMI]

It's the HVAC vents closing themselves. Normal.
Thanks. Didn't sound like a malfunction, just didn't know what it was.

[632 Regal]

no noise = bad

[Blitzkrieg Bob]

Pull over on a dark road, turn off the car, lean over to your date...ZZZt. buzzz...zzzt.....buzzz. Whats that? Uh .. my bionic schwantz babe! It's warming up for take off.

[Torque]

hahahah
Pull over on a dark road, turn off the car, lean over to your date...ZZZt. buzzz...zzzt.....buzzz. Whats that? Uh .. my bionic schwantz babe! It's warming up for take off.

[dacoyote]

Pull over on a dark road, turn off the car, lean over to your date...ZZZt. buzzz...zzzt.....buzzz. Whats that? Uh .. my bionic schwantz babe! It's warming up for take off.

Best line ever...