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Discussion Starter #1
my rear passanger side Mach 460 is acting up. I have a 1998 cobra with the Mach 460 stereo but changed out the head unit to an aftermarket cd player. Sometimes while driving i will get a low hissing almost like an alternator whine but the pitch doesnt change. One day i opened the trunk and fiddled with the black Mach 460 passanger amp plug....just wiggled it a bit and the noise goes away....everytime the noise comes back i do this and it goes away. Is the amp going up? Also my front left speakers seem to fade the highs in and out throughout my driving. I took it to a circuit city and they said the Mach 460 amp is causing that and that it is going up......i need a new one. Any ideas on what could be wrong?

Can i replace the amp with an aftermarket one or where would i go about trying to find a replacement rear Mach 460 amp? Dealer?
What is the cost?
 

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hmm, you're in maryland. I have the stock amps out of my 2002 GT. They are just sitting in the garage. You need the entire thing, amp rack and all?
 

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The Mach460 system uses different input voltages than the aftermarkets. The only way to change over is to buy their amps, or go with a complete system. I believe there was some conversations in the audio forum here about harness adapters that are made for the Mach system. You cannot use something off the shelf. I'm not sure if your amp is going, or if you may have some loose connections in the amp itself. You can always take the amp off the rack to see first. Then try your dealer. :sadcry: But if you ask enough questions about the system, which the average Ford tech really knows nothing about, they may point you in the direction of their Mach electronics distributor. (I did this once, and they supplied with the name and number and saved some money) You know, baffle them with logic.....
 

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If you changed your head unit, your going to need to get rid of your stock amps. You can still use your speakers but they need to be rewired. You also wont be making any kind of bass without the amp. Your best bet is to spend about $400 and have somone rewire your speakers and put a small sub in the trunk.
 

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I just went with the Mach460 system, and put in an infinity sub and amp. It sounds really good. Hits as hard as most others without ripping everything out. The surrounds work well for bass. If you want better lows and clearer highs, take out the stock speakers and add infinity components.
 

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doesn't the mach 460 have a couple amps. I was thinking four.
 

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Depends on the year, but as far as I know they all have at least 3... the 04 had the tweeter amp (4 ch) connected as part of the head unit and each of the back amps supplied power for it's respective side (2 ch each).

I think the 98 had the tweeter amp on the floor behind the head unit near the airbag controller. There is a converter (it has sliders and such) that you can hook up inline to the rear amps to alter the signal going to the amps. Those amps require a little more than line levels.

The whine you are starting to get may be from a faulty ground somewhere for that particular amp. Can you tell if it's just on one side or the other? If it's on both, it's probably your head unit or the wiring.

From what I know, you are lucky to have a 98 Mach system, the 04 didn't have a harness for about 2 years and it was completely different from the other years. Cost me 300 in labor to completely rewire the car front to back in 04.
 

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Discussion Starter #10
All the speakers in my 98 are the stock mach system........i did however put in an aftermarket JVC head unit.....maybe the 2003 model...i have a JL audio 10" subwoofer box and amp hooked up for the lows..........i have the headunit bypassed so that it would work with stock components.......thats what i was told......i never had a problem until a few weeks ago...........only the front left speakers fade in and out...its like i will here the highs coming out and then they go away.......then they come back.......and i get this whine coming from the stereo........not sure where.............when i wiggle the passenger side amp in the trunk the noise goes away..........what speakers does that amp control? Do you think its the amp or the ground wire?

How much would you want for that amp?.........thats all i need...and you said its the Mach 460 amp, correct?
 

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Now I'm really confused..... The right amp in the trunk serves the right side lows in the car, the left side controls the left. I believe there may be something else going on. There could be a short in the wiring going to your amps. They never used the trunk amps for the highs. Unless whomever put in your head unit changed things around, which is highly unlikely because the wiring for the mach's are a mess to deal with. You could try hooking up another amp and see, but it must be a grounding problem.
 

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Discussion Starter #12
ok...........you are probably right....from what i was told is that if you want to replace the stock cassette/cd player with an aftermarket cd player you have to bypass the factory amp with a special plug in harness....that is what i have done.........what does this due........are all 3 amps still powering my system?

I just dont understand how when i move around the black plug in the right side trunk amp that the speaker noise disappears......its almost like plugging an electric guitar into an amp.....that scratchy, buzzy noise it makes and then the noise is gone....should i just replace that amp or check the ground? How do i know where the ground would be connected to?

As far as the front speakers fading in and out intermittently what does that sound like? Its like i will have highs coming out for 10 minutes than they will disappear for 5-10 minutes then come back.....well there is no exact time it cuts out for but i dont think the speakers are blown.
 

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If it sounds like plugging a guitar in, it could be a loose wire.

Also when using the harness, it may still be using the amps, but may not be routing the signal the correct way. If you do a fade back to front and balance r to l, does it all line up the way it is supposed to?

If you didn't bypass the amps yourself with new wiring, then what that harness is doing, is sending a speaker level signal to amps that require line level signal. That will screw an amp up. Unless your harness accepts RCA lines from your head unit and routes them to the amps...

I dunno, like I said, mine was such a pita that I just rewired the whole thing.
 

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Okay jzepp, it sounds like you have a grounding problem. I don't think getting an amp may fix it. I guess you have to go into the trunk to see if you can emulate the sound. Does the fading of the highs coincide with the humming in the lows? I wish I still had the diagrams of the mach system to see if there is a common ground. I know with all the voltage step-downs on the amps that there must be a common ground that is messing your system up. It could also be your new harness. Yes, it does not explain the plug, but the ground going to the plug can be the same for your highs. You need the schematics at this point to find that particular ground. A dealer may be able to give you those for free. Remember the days when you only had a couple wires to install a stereo? Wish you lived closer, I love a real challenge when it comes to crap like this.....
 

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Discussion Starter #15
yeah shiner.........i wish you lived closer also.......i love installing stereo systems but not troubleshooting them. I bought the harness from crutchfield.com.......i was told by them that this is the plug that you are suppose to use on all mach 460 systems when you install an aftermarket headunit.......it bypasses the amp......now does it bypass all 3 amps? i dont know.......i pulled the plug out on the drivers side rear amp and speakers were still working.........i couldnt get the plug out on the passenger rear amp.........what does that mean?

I also noticed that my 2 front door panel speakers arent even working....just the window sail tweeters.........could that be from installing the amp integration harness?
 

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Now I'm confused more than ever. Did the front subs ever work, or are they not working now once you pulled the plug on the drivers side rear amp? What type of head unit do you have? High powered? I'll bounce around Crutchfield, but I can't see how it could bypass one amp and not all. Stay tuned fans......:bounce2:
 

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Discussion Starter #17
sorry to be so confusing...........when i bought the car i never bothered to listen to the door speakers to see if they ever worked.......just assumed they did because the window panel tweeters were.........so to answer your question they dont work now..........not sure if its because of the amp bypass plug or not........when i unplug the drivers side rear amp.........all the speakers work except the door speakers which dont work no matter if the amp plug is in or out...........the passenger side amp plug is missing the bottom piece to push up to pull the plug out so i couldnt get it out by just pulling on it...........i am curious to unplug it though to see if all the speakers still work..............that would mean that all the amps are bypassed?
 

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Discussion Starter #18
I have a high powered JVC head unit..........i think like 50 watts per channel RMS............so in essence is my head unit amplifying my speakers now? But like i said my passanger amp makes a noise sometimes and when u wiggle the plug it goes away so that would mean that its still hooked up, correct?
 

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No, it's not your fault about the confusion. I'm more puzzled about the amps. I'm thinking your amps must be bypassed simply because it doesn't make a differnece if your amps are plugged in, yet vibrating the plug changes the tones. Hmmmm. You would definitely notice the difference if the front door subs were not working. They thump pretty well under normal conditions, unless they rigged it somehow.
I looked around on Crutchfield, and the only harness that I found was for a basic radio set-up. You just plug it into the stock harness, and wire it to your radio. It would use the basic wiring structure, but not sure if it would go to your amps. The mach system uses low voltage signals to the amps, not typical wattage to speakers. Did you have alot of distortion when turning it up?
 

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Discussion Starter #20
Shiner.........if you go to www.crutchfield.com and type in ford amp bypass under keyword search at the top it will yield 2 results. I have one of those wire harnesses that have an amp bypass plug. It says this harness bypasses your factory amplifier. So are all 3 of my amps bypassed? What is amplifying my speakers now? My head unit or nothing? That still doesnt explain why all my speakers work except for both front door spearkers..........like i said i dont know if they worked before i switched out head units but they dont work now................How can i test them to see what is going on?

Also i wiggled that black plug on my stock passanger amp and pulled it towards me a bit and that speaker hissing or whining hasnt been there for 2 days now...........
 
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