Need some advices please.

I got this alternator whine on my 2013 R58 JCW coupe with OEM factory Harmon Kardon system. The whining noise is rev dependent coming from the passenger side front A-pillar tweeter. Noise is there no matter the stereo is on or off. The car has been back to the dealership for 2 days now.

Day 1: Tech heard the sound but needed more time to diagnose.
Day 2: Service advisor called back claiming they cannot hear the sound now, even with the shop foreman tried. It seems now they want to just return the car claiming the problem as "un-replicable". But the problem is consistent and not intermittent.

I understand this is a grounding problem somewhere which is tough to track down, especially this is the OEM system. If it makes the noise no matter the stereo is on or not, it might not be a problem with the stock headunit or amp, right? Other thoughts? I will visit the dealer after work.

Any ideas on what to check please? Thanks a lot in advance.

 

Go to the dealer sit in the car and show it to them again so they can't say they don't hear it.

 

It is the AMP! My JCW is in the shop now for the same. Ping me for details

 

Just PMed you for details. I went back to the dealership yesterday and finally got the shop foreman to acknowledge the noise. They kept the car and will diagnose further. He tends to think the power cord was ran too close to the tweeter wire. But I suspected it might be the amp not grounding properly. Anyhow, I need to wait for the shop's diagnosis.