alternator noise, general noise

Just finished putting an entire system in my 04 chevy crew cab.  Consists of: Sony CDX-MP70 h/u, polk momo 6.5 components, dual downfire box for 10's, 1.0 farrad cap, and a kicker 550.3 (3 channel with dedicated class d sub output).  I did most of the install myself with some help from the local stereo shop.  Fired it up and BAM...alternator noise like crazy, even some light noise with just the acc on.  I know the most likely cause of this is improper grounding, but the shop took care of that part and i watched them ground it to the rear seat lug.  Should be sufficient, right?  They did run the power and rca's down the same side of the truck.  I asked them and they said they do all installs like this and they never have a problem with it.  Also i used the walmart version of the GM adapter to keep the chimes and RAP.  it was 30 bucks less than the one at the stereo shop, looked and installed exactly the same, so i used it.  The RAP works, but i do not have the chimes anymore, not a big deal but could that indicate a problem?

One last thing.  I have had this h/u in my boat for a couple of summers.  When i first installed it there it had alt noise then too.  A friend told me to run it a dedicated power wire.  I did and it fixed the problem.  Could this be the problem with my truck?

Please help!  Thanks.

forbidden wrote:

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Read the grounding sticky, matter of fact print it and take it to the shop. Any good installer is willing to learn something new. To me it also sounds like there is something fishy with the cd player. Try a different one to see what happens. Regardless, get the ground looked at asap.

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Just got back from there.  Tried running new rca's (helped a little) away from the power wire, tried different deck, checked the ground...nothing will cure it...except (and here's the strangest part) running the system off the RAP ONLY.  i.e., start the truck, shut it off and use the retained power only.  if the key is switched to acc or on, or if the truck is running....bam, noise comes back. 

We did also try a ground loop isolater and didn't think it did anything because the noise had stopped.  We didn't realize then it stopped on its own using the RAP.  Think i'll try the ground loop isolater again tomorrow.

any help.....THANKS!

Jay T] wrote:

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hielded RCA's?

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yes, of course

Jay T] wrote:

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hielded RCA's?

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yes, of course

sparkie wrote:

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For starters, the seat bolt is usually not a good ground. They usually have all kinds of crap on the bolts preventing a good connection. Keep the amp ground cable short and the same gauge as the main power line. Connect the ground to a clean and paint free section of the body that does not go through to the outside of the vehicle. If it does, it will eventually corode. Try installing a new ground wire for your head unit to a good ground as well. Run your RCA's as far away as possible from any other vehicle and power wires. Make sure that your battery terminals are clean and tight. Clean the main battery ground to the chassis. I guarantee that it needs attention. It is located above and to the driver's side of the driver's side tow hook on the front bumper. Clean and sand it to make a good connection. Coat it with rust proofing afterwards.

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ok. sure i will try it, but this is a brand new truck with 11,000 miles and dual batteries (duramax diesel).  also, why would the ground connection from the special gm module not be adequate?  if these are common problems surely others with chevy duramax's have had them also

thanks.