mach 460 sound system help

[968]

i finally got my car up and running. it's a very nice ride - my first mustang.
i just got back from vacation to find a dead battery and now my woofers won't work with the mach 460 radio. the upper full range speakers are good (as good as they can be), but the four lower woofers are not coming on. the system is pretty pathetic w/o the woofers.
i'm pretty sure i have a mystery short somewhere that caused my battery to die. i'm hoping the two are related.
i searched the fuse boxes for the one that goes to the rear amplifiers, but couldn't find it. i'm guessing that the woofer amps are the two silver boxes behind the rear seat next to the convertible top motor....???
i didn't see a fuse on the amps (like a normal amp would have) nor did i see one anywhere else. the amps may have taken on moisture since my top leaks a little, but they don't look fried.
any help would be appreciated. if i had more cash, i'd just replace the whole system. on the other hand, i'm old now and don't need anything crazy. so if i can get the stock system back up and running, i'll be happy.

[OsirisGuy]

Check all your fuses, sometimes the least obvious one is the problem.

Have you updated any part of the audio system; the radio, speakers?
Have you changed any of the other electrical in the car?

[968]

i've checked all the fuses - at least the ones under the hood next to the battery and the ones under the steering wheel. the ones under the steering wheel are a real bear to check. i wish they were somewhere else...
the stereo is a stock mach 460. i did notice that the p.o. changed the front door woofers to pioneer 5x7 3-ways. he must not have realized that location only gets bass tones. the head unit and cd player are stock, and the rear speakers are stock. all the wires are original. i have not pulled the head unit b/c i don't have the ford radio removal clips.
the woofers were all working just fine until this week. i'm guessing it's a moisture issue, but was hoping that there was a fuse somewhere that i could check first before pulling the amps. i tried checking for power at the wires at the amp, but it's not clear which wire is which. in the process, i managed to blow the fuse to the head unit, so i found out the the wiring is very sensitive.

[modular2valve]

i have the factory amps if u need them.

[OsirisGuy]

What year is your car?

I'd get some metal hangers to remove the radio, or pick them up at an audio shop and check behind. Are all the amp plugs properly plugged in? You might want to check to see if the amps are getting power.

Also, if the speakers were changed check to make sure the terminals are connected, and connected properly (aren't slipping off or touching each other).

[968]

thanks for the replies. the car is a 2000. from what i understand, it's the last year of the separate cd player/tape player units in the dash.
i hate to pull that darn door panel (again!), but that does seem like the logical place to start. i worked in the area around the front speakers when my window motor was stuck. maybe i loosened the connection to the woofer and it's shorted or something.
as far as checking the amps for power, i tried, but there's a mess of wires back there and i'm really not sure which wire is the power wire. sounds silly, you'd think there'd be a big red positive wire or a group of smaller red positive wires going to the amps, but there aren't. there must be a circuit/fuse for those amps somewhere, right?

modular- i saw your posting for the mach amps last night on the items available section of this site. i was going to pm you, but figured i'd make sure these amps are bad first. do you by any chance still have the front door woofers from your system? i don't think the pioneers the p.o. put in my doors are suited for the mach system very well.

[968]

i pulled the two amps behind the rear seat. the one on the passenger's side under the leak in the top is fried. i should have just removed it while i'm getting the top fixed.
the power for the amps must just come through the radio circuit. there isn't much of a power cord or even a power supply in the amp.
if you look toward the top of pic4, you'll see on each side of the coil that the components are black.
pic3 is the amp from the dry side. it appears to be okay.

[OsirisGuy]

The power wires running to the amps are not like aftermarket systems. The power runs out of the headunit with the speaker wires and remote turn on and into the amp. If you can switch the amps and the problem reverses (woofers play, tweeters do not) then it is definitely a bad amp.

In the meantime you can get a little bit more info from here:
Mach 460 Information

[968]

i hear you on the amps.
the full range uppper speakers are powered by the head unit in my system. i disconnected both rear amps and they still play loud and clear.
i tried playing with one amp or the other and the best i can figure is they must work together somehow. i tried a volt meter on the wires and kept blowing fuses so i stopped.
i never would have figured that there were two amps for the woofers. my guess is that one is for the back and one for the front, but it wouldn't really matter because the two amps are exactly the same. they may go right and left.
i did check the resistance on a couple of the rear speakers. the full range uppers are 4 ohms. the lower woofers are 7 ohms, but that may very well play out to 8 ohms.
i wonder if when the p.o. replaced the front woofers with 4 ohm full range speakers if that blew out the amps.
i'll check out that site in the mean time

[OsirisGuy]

No the speakers should be four ohm, and yes I believe one amp is for the front and one is for the rear.

It's hard to trouble shoot over the internet, live anywhere near Long Island, NY? I'll take a look at it for you

As for blowing fuses when you test the leads, that shouldn't really be happening. Are you using an actual voltmeter or a test light? Are you testing the pins in series or parallel?

If it's all the woofers that are out it either means both amps are bad, or you have more troubleshooting to do. Make sure that the pins you are testing are the correct ones. Ground the meter to the chassis and probe from behind the plug and not where it plugs in.

[968]

just checked that web site. very helpful, especially on the wiring diagrams.
i'll check to make sure they're getting power.
any idea where the ground point for the rear amps would be? looks like ground #205.
after looking at the schematics, i'm guessing that there isn't a remote switch wire for the amps, but the full power comes through the yellow wire. then all the other wires are speaker wires.
after looking the wiring diagram over, it doesn't make sense that if one amp burned out that both wouldn't work. i'll have to check the power wire since it's in common for both.
i'd also imagine that four ohm speakers in the doors would be a bad thing for these amps. i doubt they can handle the extra power/current.

[OsirisGuy]

Ground to the chassis and check, not the pins.

If the fuses are blowing then they should be getting power. If you can borrow an amp or if you have a spare speaker and can tap onto the audio wires to check that could solve some problems as well.

Again the ohms shouldn't matter for this particular application, unless the previous person did a rewire. It's also possible that the previous owner had an aftermarket headunit and just went back to stock.

[968]

just checked the wiring. much better results with the schematics off the website you recommended.
the three purple/blue wires are battery positive 12V. the schematic shows them as yellow. this is the only difference that i saw from my car.
the three black/green wires are all ground. there is a fourth black/green wire which is the ground for the speakers.
that is where it doesn't make much sense anymore. the brown/orange and light green/black wires in the other bundle are ground. that much is pretty clear. then the other wires are all 5V. my only guess is that there is a stereo signal coming into the amplifiers which then kick out mono bass signals. there is a 4ohm resistance across the positive wires. i wonder if this is a speaker level input for the signal to the amplifier. must also double as a remote turn on/off.
either way, i'm pretty certain that the wiring is okay and the amps are the issue. i just can't figure why if one is blown, the other won't work.
thanks for the offer to swing by, but i'm in middle tennessee, so it'd be a heck of a drive!
i'll see if i can get my hands on a couple used amps. if not, it'd be a good time to replace the stereo. i certainly have no beef with the existing one.

[968]

modular2V - can i take you up on your offer for the amplifiers?
also, does anyone have front door woofers?

[OsirisGuy]

When you unplug the amp, you can try "jumping" the audio wires, thus bypassing the amp and making sure your speakers work and confirming your amp is defunct.

Someone else just recently had two bad amps they replaced. As for new speakers you can try and get a nice quality pair from JBL or Infinity, a decent pair like Pioneers or you can try a regular electronics store like radio shack or All Electronics | Electronic and Electro-Mechanical Parts and Supplies at Discount Prices or even Pep Boys or Advance or Autozone should carry replacement speakers.

[modular2valve]

i just pm'ed ya 968, and i would also run aftermarket door speakers.

[968]

thanks for the replies, gentlemen.
the car already has aftermarket door speakers. they're mid-grade pioneers. they look like 3-ways to me. it doesn't much matter because with the mach system, they only get bass input, so the woofer is the important part.
here's my concern with the aftermarket speakers... the stock speakers are 7ohm. my mutimeter may not be terribly accurate, so they may be designed at 6 or 8 ohms. they are wired in parallel, so bridged, they would go to 3 or 4 ohms. aftermarket speakers are 4 ohms. bridged they would go to 2 ohms. in the old days, amplifiers were not all 2 ohm stable. so my concern is that the front door amplifier got fried due to too low of resistance from those front door speakers causing too much current to flow through it. with an aftermarket amp, this would not be a concern, because most will tell you they are stable to 2 ohm, or even have a switch on them to tell them you're running 2 ohms. i may be totally wrong on this one... ford/sony may have designed these amps to be stronger than they look, but i really doubt it.