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Jzepp300 07-10-2006 05:54 PM

rear Mach 460 amp
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?

markwondi 07-10-2006 05:57 PM

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?

shinerstang 07-10-2006 07:43 PM

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.....

gdiddy 07-10-2006 09:56 PM

How old was the aftermarket stero u put in?

GTStang31 07-10-2006 11:22 PM

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.

shinerstang 07-11-2006 09:01 AM

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.

blueoval 07-11-2006 09:56 AM

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

theJam 07-11-2006 10:37 AM

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.

shinerstang 07-11-2006 12:28 PM

You are correct. There are 3 amps for the 460, and 5 amps for the 1000. The tweeter is behind the head unit, and the other 2 are on the surrounds.

Jzepp300 07-11-2006 01:00 PM

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?

shinerstang 07-11-2006 02:03 PM

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.

Jzepp300 07-11-2006 04:43 PM 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.

theJam 07-11-2006 05:50 PM

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.

shinerstang 07-11-2006 06:37 PM

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.....

Jzepp300 07-12-2006 11:14 AM

yeah shiner.........i wish you lived closer also.......i love installing stereo systems but not troubleshooting them. I bought the harness from 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 bypasses the 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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