Mach 460 ground/engine noise? - Ford Mustang Forum
 
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post #1 of 14 (permalink) Old 04-30-2012 Thread Starter
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Mach 460 ground/engine noise?

This is very strange but anything can happen so i own a 2003 mustang cobra just recently purchased i noticed the passenger amp was unplugged so i plugged it in.After cranking on the car i realized why it was unplugged because its making a squealing noise at the rear speakers.So then i purchased 2 new mach 460 amps assuming it was bad amps this was shortly after i checked all the fuses were fine of course. After installing the new amps i got the same ground noise coming from the back speakers the odd thing is that when i open the trunk the noise cuts out permanently and as soon as i close it and start driving it turns back on. I checked to see around the trunk was maybe smashing some wiring but nothing is getting smashed so i am clueless any tips would really help sounds like i have an alien mopping in rear speakers.


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post #2 of 14 (permalink) Old 05-01-2012
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Never figured it out but I had that on my 01 GT. Mine was random but seemed to mostly happen when it got cold.
If the trunk open makes it go away try disconnecting the trunk light. That is the only thing that changes electrically when you open the trunk.

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post #3 of 14 (permalink) Old 05-01-2012
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Whenever you open or close the trunk you are changing the electrical characteristics due to inadequate grounding of the lid. Install a ground wire from the trunk lid to the chassis. Also ground the amps and any other metallic part of the sound system.

And don't asume the threads of a sheet metal screw are an adequate ground. Use grounding washers and grind the paint off where the washers sit, then prime and paint over the tightened screws.

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post #4 of 14 (permalink) Old 05-01-2012
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On mine I figured it was a ground issue and I did run a wire from the battery ground to the amps but that was not it. Nice that he found that it is linked to the trunk. Mine was a vert so I had to take the back seat out to get to the amps, not go through the trunk. Never tried opening the trunk when I was troubleshooting it. Makes me wonder if it was the trunk...
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post #5 of 14 (permalink) Old 05-01-2012
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You can never be too rich, too handsome or have too many grounds.

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post #6 of 14 (permalink) Old 05-01-2012 Thread Starter
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Quote:
Originally Posted by Yadkin View Post
Whenever you open or close the trunk you are changing the electrical characteristics due to inadequate grounding of the lid. Install a ground wire from the trunk lid to the chassis. Also ground the amps and any other metallic part of the sound system.

And don't asume the threads of a sheet metal screw are an adequate ground. Use grounding washers and grind the paint off where the washers sit, then prime and paint over the tightened screws.

This makes it sound like its the actual fix lol is it normal for cobras to do this with the stock mach 460 or did i just get a funny one? I'm kinda picky and would probably not like to screw holes in my cobra or even sand down the paint anywhere in it unless i had some feedback from someone who has had the issue with the car and did what you stated and got rid of the problem.Reason is if i drill holes and grind off paint and don't get rid of the ground noise its gonna make me very unhappy and with extra holes in my car hahahah. If possible can you show me an example of what i should do properly maybe a picture or quick vid would help.

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post #7 of 14 (permalink) Old 05-02-2012
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If you have a light on the lid of your trunk you already have a ground. Take that screw out, clean it up and reinstall it. See if that helps. Then use test wires (two alligator clips connected to lengths of wire) and connect that screw to the body of your amp. See if that makes the buzz even less.

You can install a permanent ground in hidden areas. This guy here is installing proper grounds on existing connectors inside his trunk.

Installing the new ground wires - YouTube

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post #8 of 14 (permalink) Old 05-02-2012
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When I started trouble shooting mine I was using a long piece of 12 gauge wire directly connected to the ground at the battery. When I tied it to the amps I ran it under the car and up through a hole in the body then tie wrapped it out of the way.
I was just making guess though because mine was inconstant and when ever I went to work on it it was gone.

For your light it seems like a ground problem caused by it actually would show up when the light comes on since the circuit is closed. So it might not be the light is the problem rather it might be that something else has a bad ground and the light when turned on is fixing it.
See if disconnecting the ground of the light makes the buzz come back when it the trunk is open. that would indicate to me that something else is the problem.

Electrical issues always drive me nuts.

Mine only happened if the car was running so if I had the ignition set to On or Acc there was no buzz. I started thinking it was some component running the engine was going bad.
I stop trying to figure it out because it got to summer and since the buzz only happened when it was cold it was gone until the next winter. Then I unfortunately wrecked the car.

Wish I could tell you I solved it and how.
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post #9 of 14 (permalink) Old 05-03-2012 Thread Starter
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Here is a short video of the noise it is making , today I will be trying all of your suggestions.Another thing a shop told me it could be is my aftermarket alarm that is installed might be pulling ground from a wire that its not suppose to reason being that my car only does this noise when the car is on also it does it louder as the car is idling.When driving at average speed of 40mph the noise decreases but remains.Another thing they said was that the Head Unit(stereo) could probably be sending out a bad signal to that specific amp and they said to ground the headunit chasis to the car chasis to see if that helps. Any how heres the video .03 cobra engine noise rear speakers - YouTube

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That sound would drive me nuts. Yes ground your head unit and your alarm too. You can never have too many grounds.

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post #11 of 14 (permalink) Old 05-06-2012 Thread Starter
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Alright so far i have tried grounding the trunk and nothing,then i tried the amps nada , final test was grounding the headunit and got no success either.I said screw it i began to mess with the alarm and seems to be lik that gonna be it i yanked the cables around and didnt get noise for like 2 days but now it came back so im gonna remove the aftermarket alarm and see how that goes. Any ideas how much it is to get the alarm removed and leave the factory one operating?

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No I have no clue how either alarm operates. When you "yanked cables" on the alarm you probably got a good ground or connection for a while. Try disassembling, cleaning and assembling those connections, especially the grounds.

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post #13 of 14 (permalink) Old 05-07-2012 Thread Starter
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Quote:
Originally Posted by Yadkin View Post
No I have no clue how either alarm operates. When you "yanked cables" on the alarm you probably got a good ground or connection for a while. Try disassembling, cleaning and assembling those connections, especially the grounds.
I intended to do so , but I think im just gonna let someone more Alarm savvy remove the entire thing and leave only the factory one operating, my next step after that is gonna be replacing the headunit.

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I have the same problem in my 1994 GT. Did you ever find the root cause? I've replaced all 3 amps and the main unit. I'm stumped on what to do next. Any ideas?
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