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It's power is being pulled directly from the battery using 8 gauge wire. The ground is mounted to the chassis at one of the two rear seat bolts. The ground is using the same 8 gauge wire. Later tested it using a temporary run of 0 gauge straight from the battery negative.
The ground connection to the seat bolt is a poor return ground path to the battery for the amp.
You are relying on the several connection points as well as the size of the jumper that connects the body to the battery negative (ground) post.

What kind of operational results did you get when you ran the 0 direct from battery to amp?

Have you tested the voltages/idle symptoms with the amp disconnected?
 

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Discussion Starter #22
At ~1200 rpm I think we're about 14.5 volts give or take a tenth,
I'm not sure if this helps at all, but when I bring up the RPMs in mine, the voltage level doesn't go any higher than 15.1.

With my limited knowledge on this one, I know the voltage should increase at higher RPMs just like you've described, but I don't know why it wouldn't increase. Unless the PCMs regulating is failing, but currently regulating the voltage 15.1. Does that sound logical?
 

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Charge voltage won't increase if there is a large current demand - typically this would be a bad cell (or cells) in the battery.

I think it's time to back up to square one and disconnect the amp to see if everything returns to normal. FLJJ makes a good point about amp grounding, run a separate ground directly to the battery and test.
 

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Discussion Starter #24
The ground connection to the seat bolt is a poor return ground path to the battery for the amp.
You are relying on the several connection points as well as the size of the jumper that connects the body to the battery negative (ground) post.

What kind of operational results did you get when you ran the 0 direct from battery to amp?

Have you tested the voltages/idle symptoms with the amp disconnected?
I tested for resistance in the ground connection before running the temporary ground. Surprisingly it showed no resistance across any path within 3-4 feet from the connection. When I used the 0 gauge strand to double-check, it made no difference.

Shortly after noticing the voltage and the amplifier continuously going into protection from the 15v, it's been removed. The majority of the tests have been done without the amplifier connected.
 

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Discussion Starter #25
Charge voltage won't increase if there is a large current demand - typically this would be a bad cell (or cells) in the battery.
The lack of voltage increase when I increase the RPMs happens when everything is turned off. Everything that can be anyway.
 

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I work in the automotive industry and when we design products we test as high as 18 volts, most amplifiers will say nominal operating voltage is 12 to 16 volts, 15V shouldn't be shutting it down. What brand/model of amplifier are you using? Maybe the amp is bad and it caused the problem.
 

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Discussion Starter #27
I work in the automotive industry and when we design products we test as high as 18 volts, most amplifiers will say nominal operating voltage is 12 to 16 volts, 15V shouldn't be shutting it down. What brand/model of amplifier are you using? Maybe the amp is bad and it caused the problem.
It's a JL Audio MX 500/1. According to their tech support, this MX line of amplifiers were initially designed to shut down at 15v to prevent overheating. When they discovered that some side-by-side ATVs were throwing out as much as 15.1, they increased it to 15.1 (lucky me). I've installed many of their amplifiers back in the day. This issue was new to me. Smart play by them, but frustrating at the same time.
 

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Discussion Starter #29
So backing up again to the beginning - everything was fine until you ran the heavy gauge wire and installed the amp?

The alternator produces an AC voltage which is rectified (probably a bridge rectifier - four diodes) and the PCM regulates the voltage. The alternator output voltage will increase or decrease based on engine rpm and load, it's the job of the PCM to adapt by keeping the voltage constant (above a certain rpm.)

The only way I can see the voltage increasing to >=15v is the PCM isn't regulating or there is an inductance in series with your amp. From the Wiki on inductance:

One intuitive explanation as to why a potential difference is induced on a change of current in an inductor goes as follows:
When there is a change in current through an inductor there is a change in the strength of the magnetic field. For example, if the current is increased, the magnetic field increases. This, however, does not come without a price. The magnetic field contains potential energy, and increasing the field strength requires more energy to be stored in the field. This energy comes from the electric current through the inductor.

The increase in the magnetic potential energy of the field is provided by a corresponding drop in the electric potential energy of the charges flowing through the windings. This appears as a voltage drop across the windings as long as the current increases. Once the current is no longer increased and is held constant, the energy in the magnetic field is constant and no additional energy must be supplied, so the voltage drop across the windings disappears.

Similarly, if the current through the inductor decreases, the magnetic field strength decreases, and the energy in the magnetic field decreases. This energy is returned to the circuit in the form of an increase in the electrical potential energy of the moving charges, causing a voltage rise across the windings.
No idea how I missed seeing this reply from you, John. Thanks for all of the details and legwork. I will read through it all just as soon as I get a chance to sit and follow along.
 
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