I had that problem too. It would just happen when I was driving...all of a sudden it would sound like some type of alarm was going off. Then, my entire electrical system went out one day (wierdest thing ever...you would shut off the key, take it out, and the car would keep running, or, turn it off, but every light in the car would turn on). MB replaced my whole fuse block and assorted associated items, and the noise has never come back. And, turning off the key shuts the car off! So, it sounds like fixing the fuse panel fixed the problem (they may have changed that blower as well, can't remember as it was a covered reapair so I was not too involved in it) so that very well could have been associated with the blower in that area.