I would have to ask what multi meter are you using?
do you have another car battery to try that out with?
what was your initial tool that made you see it was over charging?

while I have never seen this before, and I don't see how it is possible, I won't rule out a bad battery. but typically when drawing voltage to run stuff in the car, that voltage would slowly drop not spike. lol.
So I would start with a suspect meter until proven good on another battery/car.

good basic info. Do note the female connectors he shows will not work on Chrysler products, AND get the correct crimpers for the Packard terminals.

Thanks for pointing this out!! The multimeter I've been using is the bigger CEN-TECH and it's definitely not working properly!!!
The CEN-TECH is reading almost 3 volts higher than the small red multimeter and the little charging plug!! The red meter and plug are reading the same so I'm inclined to think that those are correct!
I also tested a battery in my other vehicle with the CEN-TECH and the little red meter and the CEN-TECH is giving me 15.6v while the cheaper one is giving me 12.75v!!!!
The CEN-TECH is definitely not working properly! Crap! I'll be using the other one from now on!!!! I guess I'll have to go back out there and redo all the tests!!!!
Btw the little 12volt plug meter is how I discovered the voltage was too high!

Finding out the testing meter is defective is a huge jump on correcting the problem, or finding out if a problem even exists.

I spent several hours on day looking for a problem I finally discovered was the meter I thought was good.

The voltage is definitely still too high!
The 12v plug and meter show the same voltage!
The readings are as follows...

Thanks for the link! I'll check it out!

Ok so I redid the tests with the 'properly functioning' multimeter!
Here are the results!

Btw... The voltage drops by 0.01 volts every 35 seconds as it should!

New test results for the voltage regulator...

Say I don't get this figured out by the time I have to go to work... What's the worst that can happen driving it around at 17volts???
I need to drive a total of 25 miles round trip!

if you need to drive it tomorrow put in the bypass wire like before, your voltages seem good then.
wire it up when you leave for work, when you get there disconnect it, then run it again on your way home and disconnect it when you get there.
so it is your power wire to the vr not the vr that is the problem.
you basically are losing 3 volts at some point, where you have to backtrack the loss to figure out what part or parts are causing the drop.
I have never bothered to fix it when I Get that, I just drop in a relay to give the bypass wire a key on thing so it doesn't leave it energized when the car is off.
it all depends on the time you have to dig, but that is what I do to get rid of the problem.

That's not going to work!
I just hooked up the bypass wires like before and I'm getting different numbers!!!
Idk [censored] I did wrong! I performed the tests exactly the same way each time!
The numbers in this pic are the most recent...


All I did differently since the earlier tests is bypass a battery isolator I have on the firewall! The cable from the alternator went to the battery isolator and from there to a battery cable(pictured)... You can see the battery isolator in the background and the nasty cables that were running to and from it so I completely took that out of the equation so maybe that was the culprit and it is the vr??? You can see I'm pointing at the cable I installed bypassing the isolator... The isolator actually came with the van and had caused issues before so I replaced it with the exact same unit and it fixed the issue so I thought that maybe that's what's throwing everything off!
You can see that the alternator cable I'm pointing at goes into a strange little cluster of what use to be three fusible links one of which burnt up and I replaced with a white inline glass fuse holder. The fuse holder has a little bubble on the side from overheating but the fuse didn't pop! It's a 10amp fuse and I think goes to the ignition or something not sure....

I've also been having issues with the headlight switch and instrument cluster not working properly... I briefly mentioned in the beginning of the post that when I turn the lights on it drastically lowers the voltage and in combination with the blower fan it lowers the voltage down to between 10 to 11.5 amps!!!! At least that's what it read at the cigarette lighter with that little usb charger/meter! 7Not sure if it's related to the overcharging issue or separate but I thought I'd mention it...

I would say the meter is suspect again.
only because while the numbers are different, the result is the same.
2 posts show battery voltage regardless of the number.
This means the VR should be seeing the correct voltage vs the dip you see without the bypass.

second
all those connectors are terrible. you can see some of them look burned. poor connections and not even water proofed. I would replace long sections of that wiring where you have multiple connectors on it.

third go to an actual store not harbor freight and pick up a reasonalbe multi meter.
I have a cheap 10 dollar one that works and even though I got the harbor freight ones cheap I don't use them for anything more than checking continuity.
or run to a pawn shop and spend a few bucks more on a fluke meter.

as for your voltage inside the van, that is 2 fold.
one with the lights on and idle you get lower voltage. it is a known thing and you see it start to go higher when you hit about 1500 rpm to 2k rpm your normal driving range.
two, that lighter voltage is going to be lower and an easy way to show the drop from the bulkhead connector.

All those wires with yellow connectors that are burnt aren't connected to anything... The wire I'm pointing at eliminates all the mess you see behind it! I know, that has yellow connectors too but they're new and it's temporary....
The two posts that show battery voltage are connected directly to the battery as the diagram shows. The wires that go to those two posts are disconnected. How is the vr getting that voltage when the left and right side of the ballast resistor are isolated? The power from the bottom right connector goes up to the top right connector and same with the left side.... I'm not even sure how the vr is tied in! I'll have to check the diagram to see how that all works! Please be patient, electrical is very confusing for me!!

As for the multimeter those are expenses I can't afford! I can't just walk or bike to the store either! I live rural and the nearest store is Ace and that's about 26miles away so I have to drive the van! My other vehicle has a bad clutch and that's why I started driving the van!

Am I doing the bypass wrong??? When I run wires directly from the battery to the ballast I unplug the bottom wires from the ballast and leave them disconnected while having the hot wires from the battery to those two posts! The voltage the top two posts show are in direct relation with the voltage being fed at the bottom posts....
Am I supposed to have the two wires connected to the ballast while also feeding direct power to them?

I'll go out there again once I've had my coffee and check the meters... They can't all be bad!!! That little red one that's the one that supposedly works good is new! This is the first time I've used it! I'll compare it to the CEN-TECH and see the difference and try and do those tests again....

What's the worst that can happen by driving the van with high voltage??

Danger..I ruined a red top battery in my car when running 16 volts on my car in no time. Case on battery was bulging and battery went dead..

as mentioned above you start to cook the battery. so you would eventually have to replace the battery due to damage.
as for the bypass, you shouldn't disconnect any wiring.
you are just adding a wire to the ballast.
you should find in the wiring diagram that the ballast shares power with the input to the vr. and one of the field wires to the alt.
the second field wire is what is controlled by the VR.
so when you add the bypass, it puts the sensing voltage from the ballast with battery voltage correcting your drops in voltage as it travelled.
so it is back feeding the vr with power you added to the ballast.
a more permenent solution is as I mentioned to use the sensing line to fire off a relay and then providing the vr/ballast with battery power directly through the relay. takes out all the connectors.
but you can clean it all up as well.

https://mymopar.com/wiring/
they have 79 truck there so it should work.

Yea I figured as much with damaging the battery... I hope I haven't caused too much damage already, it's brand new and I've probably driven about 200 miles with the voltage at 16.5 volts! I didn't have another option though.....

So I've been bypassing it wrong then! I've been disconnecting the two bottom wires and hooking up the battery directly to those posts! It's raining so as soon as there's a break I'll go out there and try again!

Btw, I have a solar setup since I live off-grid and that means I have multiple voltage gauges like my solar controller for example so I know those are accurate! I took both my multimeters and checked my solar batteries and they appear to be working just fine! Not sure why the numbers on the van are fluctuating so much but the meters seam to be reading within 0.15 volts of each other!

I'm going to study the diagram and hopefully understand the circuitry better!
I'm trying to understand what you're talking about when you say there's a more permanent solution and to fire off a relay using the sensing line... You're talking about one of the wires off the ballast? I need to figure out which one of those is the sensing wire and what relay you speak of...
Either way I think I need to just start following wires and cleaning connections!

I'll get out there and do the bypass properly and see what happens and brb.... Cleaning all the connections is going to take a little while...

I downloaded the 79 Dodge truck file but it doesn't have the bulkhead diagram....
I already have the Haynes manual and I've been using that manual for years! I'm familiar with the diagram in it and it's seams to be an exact match to my van!

Also, maybe check the wires at the ignition switch plug at the base of the column and under the dash. Sometimes the plug and the wires melt and can cause issues. That was what caused my overcharging issue. Blue wire grounding under the dash harness. Mine was on a car not a truck though.

Ok! Making serious progress here!
I just did the bypass test and did it properly this time with the wires connected to the resistor and power from the battery hooked up directly! See image for numbers!
With the bypass in place the voltage is looking good at the battery!!!
It seems to work with just one power wire installed on either side of the resistor! Do both sides have to be hooked up because there is a small difference in voltage when I'm feeding power from the battery directly to the left vs right side of the isolator but it's not a huge difference!
I'm going to wire up some bypass wires temporarily so that I can at least drive!
Btw the test was done after warming the engine and the numbers didn't change or fluctuate when increasing the rpm's!
So does this mean it's definitely a bad connection or bad cable somewhere? Could it still be the vr or maybe something with the ignition?