Results today. So far.
Did a video showing that there is about 2 volts between the B+ and any ground, even with both battery negative cables disconnected and isolated. (I may or may not post videos and/or pics later.)
Had to be almost zero amps, because a test light doesn't even faintly glow.
Developed a theory that the electrolyte in the batteries had formed a film on the batteries, and that film was allowing the passage of that tiny amount of voltage. Then wondered if maybe that was also somehow affecting the charging circuit on the alternator. (Don't ask me HOW, it's just a theory.
)
Took both batteries out. Cleaned them thoroughly with baking soda. Put chicken feed bags, (because they are plastic coated.) in both battery trays, then put the batteries back in and hooked up the positives only. Then did the test again.
.02volts now. Ok, still shouldn't be there, but that much doesn't concern me at all.
Hooked everything back up, got it started up... Still have the same problem.
Did the ASI test. The results will be shown in my diagram again, in a bit... The numbers though...
0.3 then, Battery voltage 0.3 3.47
A S I
Next theory.
At rest, engine off, before ever starting... Battery voltage was over 13.6v.
Ok, maybe the battery is just over voltage, and that is throwing off the alternator?
Turn on the headlights and everything else I can turn on, to drain the batteries down to something like 12.6v.
Left everything on for about half an hour. After maybe 5 minutes, the headlights went out. I joked that they must turn themselves off.
Now I have discovered they probably burned out. The high beams still work.
Ok. Started it back up again... and had a tiny bit of success.
Instead of charging at 15.6, it was charging at 14.7
So. Now we are on a track here.
Still thinking, still forming theories...
What if the batteries are just plain bad?
The alternator is struggling to charge them. It actually IS charging them. But they are so wonkered in their guts that they keep giving mixed signals. I'm charged! I'm dead! I'm mostly charged! I'm partly charged! I'm dead!"....
I'm thinking that could cause the problem. Ok, stop laughing. It could happen!
Now how to test this?
Do what I have not wanted to do.
Take out these old batteries, and replace them with my new batteries.
The batteries in the other truck had less than 100 miles on them. Brand new.
However that truck hasn't been started in over 6 months. Maybe close to a year.
So they were down to 4.7 volts. Both of them.
I installed them.
Then took a couple hours to get them charged up far enough to start the truck.
Hooked up the jumper cables from the camry to the truck.
Took the reading with the jumper cables hooked up. It was charging at.... 15.6 volts!
Ok, now I am convinced that my multimeter is probably wonky too.
Found my analog meter, and used BOTH to do my testing from here on out.
Got them charged up far enough to start the truck. Removed the jumper cables.
Charging at 17.3volts!!! WOW! It even went higher for a bit.
But that is the digital meter. The analog meter is very tiny, and very difficult for these old eyes to read. But I would swear it was charging at somewhere just over 14volts.
Ok, I am watching the batteries now. I REALLY REALLY don't want them to boil. What a waste of new batteries that would be.
I did the ASI test again. Here is my diagram with all the new numbers put in.
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Ok, it should be obvious now, that with the old batteries in there, the readings were all wonky.
With the new batteries in there, the readings are what they are supposed to be.
Yet, with the new batteries in there and charging off the truck's own alternator the reading at the battery is over 18.7 volts.
And dropping.
Here is where I interject disparaging comments about harbor freight digital multimeters...
Yeah, the digital meter still read something over 18volts. Or right at 18 volts, after about ten minutes of charging from this alternator.
BUT... I hooked up the analog meter. The meter is very difficult for me to read, but I would SWEAR that at that point it was reading 14.2 or 14.3.
Since the ASI reading at that point was exactly what it was supposed to be as well... with that same meter... 7.0v, battery voltage, 7.0v, battery voltage... I am going to assume the analog is telling me the truth.
I think it was probably the batteries, all along.
Right now, I am taking a long break. Way too hot here.
Alternative reason for the break... The batteries read over 13volts at rest, after all that.
They were so low, that I think a bit of 'uber charge' like that, is to be expected. So now, I am just going to let them sit there for a while, and "balance themselves" internally.
IF... The batteries do settle down. And the system evens itself out... It is looking like I wasted a whole lot of time. And wasted a perfectly good alternator. All because of bad batteries, and a multimeter that lies.
Howsomever... I am choosing to take a different look at it all.
I learned a lot.
I have fortified that system in ways I may never have bothered to do, if I hadn't done all this.
I DID find a few faults in circuits elsewhere.
My "wait to start light" now works.
And I learned I had bad batteries and a deceitful multimeter.
Man, I hope those batteries even themselves out, and this problem is actually fixed.
I am going to be SO worried that the new batteries are going to boil...