[bimmer21k]

I have a G20, about 5 months old now, and I have this high pitched chirping, popping or some electrical wiring like noise that comes intermittently out of the air conditioning system. I was not sure initially where the noise came from when I took it to the dealer last time, and they said they couldn't find the noise from the dash, but I experimented and by turning off the fan to complete off, I noticed that the drive is noise-free.

It also seems like it has to do with the modes that the Air Quality and the other options in the climate control system. For eg: it is more frequent when:
- The Air fans are at higher speeds
- When Air Quality mode is on Auto. (it is least frequent in re circulation mode)
- When the A/C was actually un-checked in the driving system

About when it occurs, I am almost certain that it occurs mostly when there is an acceleration or breaking (sudden movement perhaps) and when it goes over bumps (I have 19-inch wheels), but sometimes it just happens on its own. Most times this noise comes from the center vents, but sometimes from the passenger and the driver side too.

I would want them to inspect the whole AC system end to end to find the bottleneck, I am not sure if something got into the system or there is some wiring issue because it feels like a high pitched crackle when it happens. Is this a common issue in BMW's that can be fixed?

This is my first car, so I don't have experience. Has anyone faced this kind of issue and how to tell the dealer so that I don't get turned down in a manner that they weren't able to locate the noise? Please help.

Also, another issue that I have been noticing is after parking the car, there is some rattling sound that comes from underneath the car when I turn off, and it stays for a few minutes- Is it an issue?