Great, not another stinking mach 460 thread... Please help!

dsmithwc04

Member
Jun 14, 2005
31
0
6
Indy
Okay, I have a 97 Cobra with the mach 460 and my buddy has a 94 Cobra with the Mach 460. We had the same exact problem with our system and is follows:

Tweeters work fine.
High tones work on rear deck but no mid/low on any speaker.
Front door speakers have no sound at all.

We checked the gound/power two pin wire behind the drivers side kicker panel. That fixed his problem... GREAT! However, mine looked fine.

We then switched cassette/radio and CD players to see if that was the problem. His worked.. Mine didn't.

We then replaced my 460 harness with another 460 harness. Still mine doesn't work.

We then swapped my rear amps with his rear amps. His worked... Mine still didn't.

I checked the fuse in the engine bay (25amp I believe) and the fuse under the steering column. Fuses were good with tester.

So... I've tried what I know and now I'm stuck. Does the front amp send the signal to the rear deck? I know the rear amps power the rear deck but I thought I read the fornt amp sends the signal? Could the front amp be the problem? What else can I try?
 
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wmburns

SN Certified Technician
Aug 14, 2009
5,483
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Houston Texas
So... I've tried what I know and now I'm stuck. Does the front amp send the signal to the rear deck? I know the rear amps power the rear deck but I thought I read the fornt amp sends the signal? Could the front amp be the problem? What else can I try?
Yes there is a signal wire from the head unit to the amps. It's a simple signal to tell the sub-amp to power on.

Confirm there is +12 volts on the Sub-amp pin #14 (Y). This circuit is hot at all times so be careful.

Confirm the ground from sub-amp #13 (BK/LG) back to battery negative with a Volt-Ohm meter (VOM). Should be low.

Note, there is a critical ground just behind the center console that is shared by many devices including the radio. This ground if frequently messed up during a radio install. The ground acutally has several black wires tied together. All of them are important.

On the sub-amp test pin #12(DB) for voltage (+5 volts I think). If no voltage, this would explain why the sub-amp isn't powering itself up.

Having a set of wiring diagrams would help you. PM if interested.
 

beachroot

New Member
Sep 19, 2011
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0
Having close to the same problem

I recently purchased a 96 GT with the Mach 460 system. The previous owner said he was only getting sound through the tweeters on the doors due to mostly likely a loose wire. After some research I have found countless forums saying DO NOT just install an aftermarket head unit on the Mach 460 system. He did some time ago and my best guess is that the amps are now blown. I've seen many people suggest that I rewire the speakers to bypass the amps and just be powered off the new head unit.

I was wondering if this piece would do the job for me:
FD PWR HEADUNIT REPL KIT

any input would be greatly appreciated! Thanks!
 

dsmithwc04

Member
Jun 14, 2005
31
0
6
Indy
My car is still being painted. It has been a month now so the work is going very slowly. As soon as I get it back I will be checking out the wire voltages. One question real quick. I have not checked the front amp under the CD player. Could that be causing any problems with the lack of mid and low tones? I thought it only controlled the highs am I correct?
 

wmburns

SN Certified Technician
Aug 14, 2009
5,483
439
164
Houston Texas
I recently purchased a 96 GT with the Mach 460 system. The previous owner said he was only getting sound through the tweeters on the doors due to mostly likely a loose wire. After some research I have found countless forums saying DO NOT just install an aftermarket head unit on the Mach 460 system. He did some time ago and my best guess is that the amps are now blown. I've seen many people suggest that I rewire the speakers to bypass the amps and just be powered off the new head unit.

I was wondering if this piece would do the job for me:
FD PWR HEADUNIT REPL KIT

any input would be greatly appreciated! Thanks!
Might be smart to TEST the tweeters to be sure they haven't been blown out.

What makes the Mach system so difficult to deal with is two fold. While Ford calls many of the sound systems, Mach XXX, the systems are very different between the model years. People tend to want to assume that what works will work for one model year will work for another.

The other area that gives after market installers/DIY'ers fits is how the Mach system handles tweeter and midrange filters and cross overs.

In a typical system, the tweeters have a built in cross over. The purpose is the BLOCK low frequencies from the tweeters as the tweeters lack low frequency power handling.

In the Ford Mach system, the high pass filters are built into the AMPs or head unit. Further, this is different for different model years. Therefore, there are no external cross overs needed inside of the tweeters. What happens is during an after market install is the tweeters are simply connected straight to the new system. The new system does not block bass from the tweeters and the tweeters burn up.

The other area that ppl get confused on is the difference between pre-output and line output.

It is possible to use a new head unit and retain the Ford amps. HOWEVER, the head unit must have high impedance pre-amp style outputs and be able to pre-filter the High/mids/bass.
 

dsmithwc04

Member
Jun 14, 2005
31
0
6
Indy
Okay, finally got the car back from paint and ready to tackle this mach 460 problem. I am getting a new sony deck and before I have it installed I want to make sure that my problem is not something else.

I tested for voltage at the rear speaker plugs and I got 6v on all four wires. Where is the hot yellow wire? How do I check the ground wire refered to a couple posts above?
 

dsmithwc04

Member
Jun 14, 2005
31
0
6
Indy
WMBURNS, thank you so much for your help on this and other matters. You have been a live saver. Of course others have helped tremendously as well and I thank you as well.

My problem was a brake in the power line. Took a while to find but I finally found it.

I HIGHLY recommend the head unit I got installed. It's a SONY 565UI and can be found for a decent price. You can adjust the color of the lights to any color (matches the stock green lights perfectly when adjusted accordingly) and is easy to navigate mp3's on usb, phone aux, or cd. The sound is fantastic with the stock speakers and sounds better than stock and of course it has filters to keep bass from blowing your tweeters in the mach460 system.