Originally Posted by gjkrisa
Yes the alternator will usually run all the time except in newer vehicles .
Ok that's good that you don't need to figure out if it's signal going to an external amp. Have you tried emailing the maker it shouldn't be an issue with ground inside the hu.
I'm surprised no one else is commenting on this but from this point I'd have to see pictures of what's going on and maybe a drawn out wire diagram.
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Aye I'd assume they would but if I go down a hill and take my foot off the throttle, so the ecu would cut out the fuel supply, I'd assume the alternator would be generating a current as the engine is still moving but the noise stops.
Actually maybe I shouldn't sound so confident, my browsing of forums suggests it's a grounding issue but I actually have very little knowledge of electronics. All I know is that I've taken out an Audi Rns-e OEM head unit in a car with separate OEM installed amplifier as part of the bose sound system upgrade.
There's no noise when the engine is off, the noise starts when the engine is turned on and is effected when you turn screen brightness up, and when you touch the screen. It also increases with rpm. There is a range of low and high frequency noise.
The head unit bought:
They have offered me a refund if I want it but I do actually like the unit, the sound quality isn't bad and the functionality is so good. So if it's something I can fix Id rather fix it. They've suggested using a high to low converter in what I think is using the amps amplifier and converting that input back down to use as the line input for mine but I see no point in having a good amp to do that. But I suppose that should give some insight into where the issue comes from.