Mach 460 - only tweeters F&R are working

[cougar694u]

I have a 99 GT with the mach 460 system. About a year ago I installed a new head unit (JVC MP3 Player) and everything worked fine. All the speakers were on, all 4 channels worked perfectly.

Last week, the rear amps shut off. All 4 channels still work for the tweeters, but that's it.

Nothing changed, but I checked the plugs in the back of the stereo, that's all good.

I checked all the fuses under the hood and they're all good. I checked all the fuses under the dash, all good.

On each amp in the trunk there are two plugs, one with 8 wires (guessing for the speakers) and one with 3 wires (guessing power, ground, and remote). With key on and radio on, I tested the three wires with my volt meter. When grounded to one wire in the plug, the other two got 11.4v and 6.4v, and it was the same on each amp.

Now, there's a plug directly in between the two amps with 4 wires (2 red, 2 black) attached to the black part of the 'box'. The plug comes from the harness that passes near it and then are passed into the box. They're heavier gauge, so I assumed that maybe they're the power wires, but there's no power on them, and two are grounds.

Any ideas or pointers?

 

[COramprat]

I have the same problem...if I crank it up a bit they will kick back on. There is another amp under the CD player in the dash. I'm thinking something my be lose there. Takes a bit to remove it but you can make sure all connections are good.

Here is a site that may help you

http://www.flemworld.com/Mach460/mach.html

 

[cougar694u]

Thanks. I went to that site, but it doesn't have much information I don't already know.

I searched and found a bunch of people having the problem, but no info on a resolution. I don't particularly want to bypass the amps, so I'd like to find out what's going on.

 

[COramprat]

The only other thing I can figure is one of the amps has a bad switch. It turns the amp on automatically when car is started. But the switch wouild be internal so you'd probably have to replace the amp.

 

[cougar694u]

I still haven't figured this out. I tried following the diagrams on that page listed above, but I can't follow it (guess I have adult ADD).

I found another schematic a while back, but can't seem to find it now. Does anyone have any ideas on what else to try?

I pulled the center amp and checked the wiring that and all is well, as far as I could tell.

Any tips would be greatly appreciated.

 

[MyStangGT]

Have you tried cranking the volume up as mentioned above? My 99 did the same thing but you could turn it up loud and amps would kick in then you could lower the volume where you want and they would stay on.

I never looked into fixing it and now it just gets raced I have radio and ac removed.

 

[cougar694u]

I'll try it in the morning, but how loud are you talking about? I cranked it up over half way to where the tweeters were killing me, but they never came on.

 

[thomas91169]

replace the head unit, put in new speakers (components up front, coaxials in rear) and rewire everything speaker-wise (get the metra harness so the head unit is plug and play).

it took me two years to finally ditch the mach460 setup and i am pissed i havent done it 2 years ago.

 

[2000fordstanggt]

replace the head unit, put in new speakers (components up front, coaxials in rear) and rewire everything speaker-wise (get the metra harness so the head unit is plug and play).

it took me two years to finally ditch the mach460 setup and i am pissed i havent done it 2 years ago.

i just bought my second new edge with the 460 and am planning to rip it all out as soon as my speakers get here.

 

[chrisconsin]

Is it recomended to keep the upper mach door speakers (tweeters) hooked up or just bypass em and use the lower door speaker when rewireing?

 

[cougar694u]

replace the head unit, put in new speakers (components up front, coaxials in rear) and rewire everything speaker-wise (get the metra harness so the head unit is plug and play).

it took me two years to finally ditch the mach460 setup and i am pissed i havent done it 2 years ago.

If you want to pay for it, by all means, go ahead, I can't afford that. Otherwise, I'd like to find the problem, not just replace the entire system.

I put the stock head unit back in with the same issues, so i went back to my head unit. I turned it up as loud as it would go, but they didn't kick in.

I'm open to troubleshooting suggestions (not 'replace' answers).