YES! Finally I think someone else with the same thing I hear. I searched for this a few years back, never found anything exactly like it though on here. I thought it was diff whine when I first bought the car.Anyone had their air conditioning make a weird faint whistling/buzzing noise? Turn the ac off it goes away. Very strange... My forum search was unsuccessful.
I don't think it's the blower fan in my case as with the blower on in heat mode or non recirc' mode the noise goes away.Sounds like the AC / in car air blower fan (not the AC pusher fan in front of engine bay) could be on the way out - mine is tired in my car (130k miles) and I have a new Hella one to go in. Does the noise change if you adjust the speed using the AC fan control?
My M5 has the same issue. It's definitely a whistle and not a buzzing sound. Mine will start as low as 45 MPH with the recirc button on. If you tilt the sunroof it gets MUCH louder. :-/YES! Finally I think someone else with the same thing I hear. I searched for this a few years back, never found anything exactly like it though on here. I thought it was diff whine when I first bought the car.
I've found that these things will create or stop it:
Switching A/C on or off, also switching A/C from recirculate to incoming air will stop it.
It only starts on mine when I go above 80mph with the A/C in recirc, if I turn off the recirc and/or drop below 80 it will stop.
I think also TILTING the sun roof open will stop it too. Opening it fully probably stops it but too much wind noise to hear it.
Thanks for the tip. I'll definitely check the "snorkels". Hopefully the dash doesn't have to come apart. If that's the case I'll not use recirc unless absolutely possible.Hmmm odd. So if you open the sunroof while driving along it gets worse. That means reduced air pressure in the cabin I assume, perhaps pulling more air through the vents.
Long shot, but worth checking your ac 'snorkels' that connect from the firewall in the engine bay to the cabin filter enclosures are connected properly, additional air could be being pulled in through a gap there making a noise. It's easy to damage the clips holding these on over time.
Otherwise my money is still on your main blower fan - managed to remove dash and change mine in 2.5 hours last time - a big job but strangely satisfying... it does look like your car has exploded though about 2 hours in!