Car Stereos: alternator whine through speakers, factory wiring harness, chevy silverado

Question
QUESTION: "I have a 2001 5.3L chevy silverado - Alpine head unit,equalizer, and 2 after market amps, also the speakers are all aftermarket as well / I have had this stereo for a long time - I have a whining noise through the speakers & it is very annoying w/ low volume. I have ran different RCA cables f/ the amps to the eq, and have checked ground(s) for the deck & amps - multiple times. I have changed alternators & just put in a brand new battery - no difference! I don't know if it's the amps or maybe age of the stereo - I do know that if you unplug the alternator - no noise! I have heard of guys w/ these trucks have the same problem's w/ aftermarket stereo's - what does anyone suggest???"

ANSWER: Don, Normally, this can be fixed by cleaning grounds and making them as short as possible.  If that hasn't fixed the problem, then I would suggest getting a noise filter installed on the radio's power wire.  The noise is caused by an open loop ground, which means it is easier for the alternator power to go through your radio to ground than to the battery to ground.  To stop that, the noise filter adds resistance to the power cable, so only the clean power gets through.  Hope this helps, Scott

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QUESTION: Thanks Scott - I did have a filter installed once - I can't give you any info on it because it did not work - and I am not sure if it would have been installed like you said. That should be the only fix then? I shouldn't have to get everything re-wired?

Answer
Well, if everything was wired correctly, you wouldn't need the filter.  The problem is finding the wiring problem.  It may be a problem with your aftermarket equipment wiring or a wiring problem with the OEM equipment.  There may be a bad connection somewhere on the charging system.  It is just really hard to track, once you get started on the OEM wiring.  I have had some good luck bypassing the factory wiring harness for the OEM stereo and running my own wires to power supplies and ground points.  It is also very important to have ground wires as large as or larger than the power supply wires.  I have had some pretty good luck with the noise filters to block engine noise for a pretty inexpensive fix.  Good Luck, Scott