'14 M50d Harman Kardon popping/cracking sound

[nandika]

Hi!
I recently bought a used X5 M50d year 2014 with Harman Kardon audio. Used the car for like 5000 km's after buying it, and the rear left speaker in the door started to do random loud popping / cracking sounds.
I've noticed these crackings only happen when the engine is running. I mean, I can sit in the car and watch TV for hours without any popping, but when I start the engine it starts this annoying thing...
Even when the sound system is muted or volume down.
Doesn't matter if I choose radio / tv / media it's always the same.
Sometimes on a long trip or at higher speeds it just stops doing it, sometimes it comes back randomly.

Anybody experienced the same with Harman Kardon?
Dealer said need to replace AMP, but I'm not 100% sure that's the case because it's just happening when the engine is running.

Thank you for any info regarding this!

[suitedcboy]

Eliminate alternator as cause. Remove belt and run engine and see if the popping is gone. You can also check the output lead of alternator, not at battery, with voltmeter set to AC voltage and check that AC voltage level is no more than 100mV. Rectifying diode failure can cause AC voltage to be much higher and still charge batteries and not give any messages, at least until failure worsens. The alternator is not charging at times and is doing reduced charge at times with BMW charge strategies. Highest charge is when throttle is released and you coast with injection not delivering fuel.