Charging issue makes no sense at all, driving me insane.

[rpiggott871]

Fixed! see post 3. Here's something to confuse you all. My truck stopped charging and therefore has been down for a week.
I've never seen a problem like this before, im at the point where theres nothing at all for me to do any more because everything is working fine, yet its not working

Here's what I know.

I can jump start the truck, it will fire right up and will die within a minute of pulling the jumpers off.

There are the 3 wires on the alternator. Yellow, green, and white/black. Yellow wire has 12 volts on both sides of the plug right at the alternator. Green wire has 12 volts as well. Just as they should.
White black wire is in fine condition and have checked to make sure with the electrical tester.
So we know the alternator is getting the power it needs to "Turn on" and work. So no fused wires, fuses, bad wires, etc. could be the problem because bottom line is that the green and yellow wires have 12 volts at the alternator.
The alternator is grounding fine. I have welding cable bolted from engine block to frame. I double checked the connections ,and tested the grounding with the ground test point on the alternator.
I also swapped in my buddies good optima to replace my optima in case i lost a cell and it was doing anything weird.
This points to the problem being the alternator for sure, with a possibility of it being a bad alternator to solenoid wire (big black/red alternator output wire). So I had my alternator checked. Everything checked fine. So i bought a new alternator anyways, not trusting the test. still doesn't charge. Tested everything again and concluded that it must be a bad new alternator. Returned it for another. Still not charging. So it's NOT the alternator, which also rules out the voltage regulator since it's built in. But with a good alternator and 12 volts at the green and yellow wires there is NO reason it shouldnt be charging.

Testing at the solenoid, or the battery, i get 12 volts dropping till the the computer starves for power and the truck dies (running electric fuel pump and fan so it doesn't stay alive very long).

Here's my one and only clue as to something is wrong, but this tid bit points to the voltage regulator being bad but that can't be the case, i've 3 good alternators on the truck with the same result every time. Truck running, jumpers pulled off, testing alternator output directly on the output post... i put the volt meter on 20v max and it climbs to 20 then shows a line as if its getting overloaded so i switch it to 200v max and it shows 50, telling me its putting out WAY too much power. But again, how could all 3 alternators (voltage regulators) be bad, doing this, and why am i getting only 11 volts (dropping) at the solenoid that this alternator output directly goes to.


I've had my car buddies over and they were mind blown as well.
If anyone sees anything wrong with my reasoning or has an idea please let me know I am starting to go insane and need my truck running.

 

[kimcrwbr1]

http://www.therangerstation.com/tech_library/chargingsystem.htm
do a proper diagnostic your alternator should be putting out around 15 volts when running 1500 rpm. sounds to me like the wire from the ignition switch to the regulator has a bad connection it is not telling the alternator it is using power so the alternato is not putting juice into the battery. You can also add a ground wire fron the alternator housing to the battery neg terminal.

 

[rpiggott871]

What are the chances. Just posted this then went out for one last try on it and just got back from driving it around aimlessly!

The alternator output wire had a bad connection at a butt splice the previous owner did. I went through the whole truck and cut out all the crimp splied wiring and soldered all the connections except for this ONE connection because i had missed it and guess what, it goes bad! Soldered it and i've got 14.5 volts out of the alternator.
Never assume a wire is fine...

 

[kimcrwbr1]

Disconnect the battery and fully charge the battery. It1s not good on a alternator to charge a drained battery. Give the battery a good charge and then monitor it for a week or two do the load/noload tests but sounds like you have it handled.