Car AUX buzzing/static noise

[Markec98]

I recently buyed a Opel Astra H GTC. It has a CD 70, with Bluetooth and AUX etc. So for music I used used AUX, cause the previous owner left me his 3.5mm cable, but few days ago it broke. I started hearing that buzzing/static noise like theres "no signal" when turning volume up, it is annoying. So I thought it was the cable. But even if I disconnect the 3.5mm jack from AUX input the sound still continues, so I thought it the CD charger broke. Tried switching to FM, used CD, even tried a FM Transmiter that you plug into the cigarette lighter, works fine, no buzzing/static noise etc. So the AUX is the problem, google didnt help me much, some say dust got there, some say that some wires "disconnected a bit" and short curcuit problem, some say ground loop (dont know what it means), some say alternator noise (didnt try starting radio when car engine turned off, just power on from key, will update)... I physically dont have acces to the wires that go from next to the handbrake to the CD charger or where they go, so cant do much. Anyone good in car elextric can help?