Today I went to start my 1998 740il, after sitting for over a week and I heard a whistling noise from the passenger side back seat. It only occurs when the car is cranking, not in any other ignition positions and stops when the car starts. thanks in advance for any information. Walker Thanks for the advise, I turned the a/c off and still heard the noise, but I finally was able to drive the car and could hear the noise every time I pressed the gas. I have nav system so I hope it is not electrical. thank you for all the info....