[BickUW89]

We have a 2011 535ix M-Sport. 18 months ago we had an air compressor fail, which was replaced on warranty. The second compressor promptly failed, and we finally got a third one installed, with a bunch of other work related to the A/C system. It was a painful back-and-forth experience, but our local BMW shops (Tacoma and Bellevue, WA) finally got it fixed.

Then we started noticing The Noise.

Mind you, we've owned this car for 5 years, so we know it well. The Noise was definitely not there before any of this work, but now it's there on-and-off everytime we drive the car, and it's driving us absolutely crazy. Enough so that we are seriously considering selling car JUST BECAUSE OF THE NOISE.

It is not loud, but once you notice it you can't un-hear it. It comes from within the dash on the passenger side, and sounds like white noise, kind of like what a small motor or actuator might sound like if it was opening/closing something. Except, according to two BMW Master Mechanics, there is no such device within the dash.

It manifests itself in strange ways:

- It only makes the sound when the car is in motion (the only exception: we sometimes hear it briefly when we start the car). At stop lights or when parked, whether in D or P, it will NEVER make the sound.
- The period between when the sound occurs is totally random. Sometimes every 8-10 seconds, sometimes after 45-50 seconds. Occassionally (rarely) not for a few minutes.
- The duration of the sound is totally random. Sometimes a short "sssssshhhh." Sometimes it lasts for almost 10 seconds.
- The volume of the sound is always exactly the same; never louder, never quieter.
- The speed of the car makes no difference; only that the car is in motion.
- The stereo on/off makes no difference.
- The climate control and A/C settings make no difference, including on/off, fan speeds, auto vs non-auto, A/C on-off, etc.

Now, to really drive me batty, knowing that it only make the sound when the car is in motion, a couple of weeks ago when I had the car up on jacks to change out my winter wheels for summers, I started the car and put it in drive, then sat in the passenger seat eagerly awaiting my chance to hear exactly where the sound is coming from. Bubkis. Absolutely no friggin' sound. What, the car has to be in motion AND fully weighted on the ground too? Apparently so.

It's impossible to diagnose! I've had it in to two different dealer's shops 3x each, and they all swear either that:
A) there's no sound/it's fixed, or
B) We can't replicate (i.e., they didn't even try), or
C) All F10s make that sound; it's normal. Uh, no, it's not normal. My car never made that sound before, and none of the 10 different F10 loaners I've had have made that sound.

Does anyone have a similar symptom, or any ideas what it could be? I'm really ready to drive this thing over a cliff. Over. A. Stupid. Little. Annoying. SOUND.

[bimmertaxi]

There are at least 10 to 15 actuators on the ac unit and blower unit, depending on the type of climate control.

Maybe the Automatic Air Recirculation (AAR) mode is activated.

[BickUW89]

Originally Posted by bimmertaxi

There are at least 10 to 15 actuators on the ac unit and blower unit, depending on the type of climate control.

Maybe the Automatic Air Recirculation (AAR) mode is activated.

Yeah, I had noted that system when talking to the Master Mechanic, but he kind of dismissed it. If I recall correctly, he said those actuators would make more of a popping or clicking sound, rather than a moving/motorized sound.

I can't help be come back to that part, myself. I wonder if anyone on here has any experience working on it, or knows anything about how it functions.