Faint hum
 

Does anyone hear a faint humming sound when the climate control is used. I never really notice any noise before other that the air rushing out of the vents, but now it seems like there is a faint humming noise.

Yes, I did a search

Yes, I may just be imaging things

I had something similar
they found it was the secondary pump, of some sort, under the dash on drive side, it came, and then it left, it was sitting on weak rubber bushing, which they replaced, now its silent.... the noise looked like it came true the vent

Ok. Will mention when I take for oil change (due soon)

I have the same problem, but it is not always present, specially when I take the car to the dealer.
Please let us know what you find.

Yeah, they couldn't replicate it, and it doesn't happen all the time in mine, so I'd be very interested too.

Can someone tell me what is a secondary pump? is it related to the A/C system?
Thanks.

It might be the e-box fan. Part #13 in the diagram. Mine has an oscillating hum that's very annoying.

http://www.realoem.com/bmw/diagrams/e/r/247.png

Is that e-box part of the A/C system?

No. It houses the ECU. It has a fan to moderate the temperature because it's in the engine compartment. The fan comes on whenever the HVAC fan is on and draws air from inside the cabin.

I had it in the dealer recently for some other things and I had them try to find the hum, but they couldn't of course. After I picked it up I tried to replicate it in the parking lot, but I couldn't get it to do it. It seems to happen more often after the engine is fully warmed up.