2001GTMustang

The other day I began hearing a wine that sounded almost like a blower, without having my radio on (Full Stock Mach 460 System, with the addition of an Infinity Basslink which uses the rear speaker leads to receive its signal to play). With the radio on I could not notice it, but the radio played fine and had clear bass and everything from all speakers. The next morning though the rear subs quit firing and would make random pops although the front ones play as normal. Anyone have any thoughts? Here is what I have done already to try and diagnose this problem:

-Checked all fuses
-Check to see if the amps mounted on the Mach 460 enclosure where receiving power
-Checked the Resistance at the Harnesses going to the Amps
-Checked the Connections of the rear Speakers inside the enclosure as well as connections made for the Infinity Basslink
-Visually Inspected Rear Subs
-Swapped a buddies working Mach 460 ampifier for the rear set of speakers and it did not solve the issue, and my amplifier played worked as it should in his car. (Looking at the wiring diagram for the system, the left amplifier in the trunk powers the front door subs, while the right amplifier powers the rear subs.)

**Everything listed above seemed to check out okay**
-The voltage and Resistance Checks where performed via the Pinpoint testing listed in the Factory Repair Manuals.

Sorry for the lengthy post, but this has been a frustrating issue and I would like to resolve it without doing anything to replace the Mach 460 system, because I am satisfied with its performance and like the "Stock Appearance".

Thanks for the help!

2001GTMustang

Bump...

2001GTMustang

Anyone got any thoughts? I have pretty much torn the car apart checking all the wiring going to the rear amp and subs and everything looks good. The only thing left is to check the headunit, but I really do not have a way to do that. Before I drop a bunch of money on a Mach 460 headunit and find out that was not my problem I could sure use some suggestions. That or if anyone has a Mach 460 headunit that they do not mind donating to help determine the cause of my problem I would greatly appreciate it.

01red

I assume you went back to stock, removed the extra subs before doing this testing. The less variables the better.

If you have swapped amps with freind and they work fine in his car but not yours, then you know it is not the amps. I assume his amps do not work in your car.

So it is either the head unit or the wire/connector harness.

Next step would be to swap the head unit with your friend. It should slide out when you poke hangers in the four holes "locking" the radio in.

If all the components work, then it is down to the wire harnesses. That is when the "fun" begins.

I had a problem with amps getting noisy after rain in my 2001 vert. (The engineers at Ford put the amps on the trunk floor directly under holes they put in rear deck where the water collects when the top leaks.) I cleaned all connectors with contact cleaner spray a few times. I also lossened the bolt and cleaned the mounting surface of corrosion. Music has been fine since.

Good luck.

2001GTMustang

Okay, so I am still in the middle of this no bass issue. So far here is an update on what has been done. I purchased a supposedly good headunit from a forum member and the problem still exist. I doubt that I would have purchased a headunit with the exact same thing wrong with it as the one I originally had installed. I went back through some diagnostic pin point testing out of the Shop Manuals and found that one of the wires going to the rear amplifier had a resistance less than what the manual specified. This test in the manual suggest if the resistance is less than 10,000 ohms between the harness at the amplifier and ground then the circuit in question needs to be repaired. Does anyone know a good method on how to go about checking that wire and where the wires are routed in rear seat area of the car for the audio system? Also could anyone suggest what the problem with the wiring may be causing the resistance to be less than what the manual's check requires it to be? I think the problem must be something simple, but I just cannot determine how to approach the wiring if this turns out to be the culprit.

By the way, here is a wiring diagram of the Mach 460 system (http://www.bullittarchive.com/7029.htm). The wire that is not passing the Shop Manual's test is wire 172 (LB/RD). Maybe someone can understand this and explain...electricity is not my strongest subject.

01red

I will try to help, I am an Electrical Engineer, but sometimes it is hard to track these things down over the net.

I am a little confused by the statement "(Full Stock Mach 460 System, with the addition of an Infinity Basslink which uses the rear speaker leads to receive its signal to play). " Did you add the Basslink, or was that factory installed? If after market, I would suggest disconnecting it to see if that is the problem.

If I understand, you are now getting no sound at all from the Rear Subs.

Also, you have confirmed that +12 Volts is getting to the Amp AND that the - side of the connector is connected to ground. In other words, you are reading 12 Volts between pins group 1,2,3 and group 4,5,6. (Be carefull not to short here or it will mean a new fuse.)


I am not familiar with the tech manual you are using, but it sounds detailed.

Does the manual have you disconnect both ends of the harness before taking measurements or is it connected at one or both ends?

When you say the resistance is below 10,000 Ohms, what reading do you get?
If it is, as you say, from the wire to ground and a very low reading, below maybe 100, then I would say the insulation has worn through and you are shorting to ground. If high, like 5,000-10,000, I would guess insulation on wire has gotten saturated with water or other fluid and is not fully isolating the signal from ground. This may require replacement of that wire. If it turns out to be a bad wire, you should be able to bypass just that wire and not need to replace the whole harness.

Un-fortunately, the diagrams do not indicate what signal is carried on Wire 172. This would be a big help. My guess is that it is the common ground for left and right rear lows to the amp. But this would not give you "no sound", it may reduce or distort sound though.

The wire harness is under the back seat. Just remove the bottom part then remove the two bolts for the back part if needed.

2001GTMustang

Thank you 01Red for your response, I have been out of town and am now having to face this problem again. I do not know much about electrical stuff so if you can give me basic directions it would be great.

"Also, you have confirmed that +12 Volts is getting to the Amp AND that the - side of the connector is connected to ground. In other words, you are reading 12 Volts between pins group 1,2,3 and group 4,5,6. (Be carefull not to short here or it will mean a new fuse.)"

Can you explain what you mean by this qoute? Not sure I follow what you are saying about the connector side being connected to ground.


When I first started with this issue, I checked to see that I had 12V at the pins 4,5,6 (wire 828) at both amps which I did. Then I checked to see that I had 0 ohms or very close to 0 ohms at the pins 1,2,3 (wire 694) as shown on the wiring diagram and in my shop manual.

I am actually getting intermittent sound coming from the rear subs, for instance they will play for a second or two of bass then make a popping sound and cut off for a while then play for a second then pop again. If I try to wiggle the wires at the connectors on the amps and the headunit it almost seems as if I get the subs to play a few seconds longer than when I let it sit undisturbed although I can not keep them playing or replicate the length of time the subs play when messing with the wires.

The check I did for resistances at wires 169, 172, 174 and 167, 168, 173 was performed as directed by the shop manual (which I can email you a scanned copy of the diagnostic page if you send your email to me). The resistances were within the manuals specified ranges (greater than 10,000 ohms) for wires 169, 174 and 167, 173 although wire 172 had a resistance around 500 ohms while wire 168 had a resistance around 5,000 ohms, but both were supposed to greater than 10,000 ohms. It is odd though becuase the front subs play as they should even though the resistance is lower than the manual states that it should be (wire 168 5,000 ohms).

Any thoughts on how to proceed and check the wires, and by the way the wire harness actually runs along side the rear seats inside the trim covering the rear quarter panel.

Thanks for the help.

2001GTMustang

I have also had both amps tested and the headunit tested by a repair facility and they tested to be okay. I have also hooked up a portable radio the rear subs and the basslink and everything seems to play fine.

Just to help rule out any places to look.

2001GTMustang

Problem solved! There was a pinched wire that was grounding out on the body. Quick fix after finding it and now once again rocking down the road to good tunes. Thanks for all the input and suggestions guys.