i have a 98 Ram 1500 5.2L 4x4 standard can 1/2 ton.
It reticently had a new transmission installed. When I picked it up the mechanic said the "the computer diag said my alternator was going bad and the regulator was "over charging and battery and that soon it would cook the system if i didn't' get it replaced." He said the regulator was inside the alternator. I got in the truck and noticed the volt gauge on the dash was right at the right side white line (high). I got about 2 miles down the road and the whole truck's electric system started going wacko, then it just died, no power. my battery was at no charge.
I pulled the alternator and got a new battery and new a alternator. They tested the new alternator at autozone and said it passed. I Installed both. I noticed the dash gauge was still reading high. I went to have the charging system checked again. They said they couldn't test it because the battery was dead. The battery only being hours old, I figured i had a bad battery. I returned it and swapped in a new battery. I went back to test the charging system at auto zone,... same thing, "you have a dead battery". I told the kid he might have a bad tester, he agreed and I left to put my own volt meter to it. I was only getting a 12.14v reading. I called a different mechanic I have used and he said that" i could have locked my alternator in high charge and fried my new alternator with the bad battery"....so I go back and swap out the alternator again. I charged up the 2nd new battery, installed both and still with engine off: battery is at 13.4volts (fully charged) and with engine running the circuit reads 12.8v. In a few days my battery was drained yet again.
I have found that I should be charging with about 14volts to keep the battery full. It seems my alternator (new) can't get more than 12.1-12.8 volts back to the battery (new). So my truck drives around for two days running souly on the battery with no recharge.
1. Is the alternator's voltage regulator:
a) inside the alternator ?
b) off the back of the alternator? or
c) in the computer itself?
2. what is the black box on the wiring harness attached to the back on the alternator?
3. I've read that the PCM computer on these is virtually indestructible, if it is the cause of the volts issue, how would it get messed up sitting around waiting for a tranny install?

 

The voltage regulator is inside the PCM. There is a way to add an external one but I don't know the links.

 

Can anyone tell me what this is? because this is what the back of my alternator looks like ,exactly. Could my PCM have gone out before I got the truck, and the previous owner installed an older voltage regulator to bypass this problem, which has now failed?
Because I can't find this part which is hooked onto the back of my alternator and to me, it looks like an external regulator.

 

It sure looks like an external unit. Did you switch that over to your new alternator?

 

Hmmm, maybe it's not. In this tutorial, it has you remove it but it has the reg inside the PCM too.

https://dodgeforum.com/forum/1st-gen...onversion.html

 

Reading through that thread, one person had blown the 120amp fuse. You might want to check yours too.

 

Look over your wiring. They pinched or pulled apart something when they rebuilt your tranny. Maybe they didn't hook up some ground wires or connect the wires properly at the starter. Take off both ends of your battery cables and clean them. I doubt it's a coincidence that it's acting up after the transmission. It almost seems like there is a short some where.

 

Yes, I did use the little black box when I switched out both alternators., but you are right it doesn't look like standard new "regulator modification.", but they do say to set it aside as you will not be using it after the mod.....of course they don't state what the thing is.
I did look at the 120 amp fuse, the window did look a bit discolored, but it didn't look blown from what I could see. But if that was blown, would I still get the 13, 12, and then 9 volt readings as the battery drained?

The other odd thing is the dashboard volt gauge reading so very high at every stage. I've tested it "the circuit" and we have had nothing over 12.4volts, why is that meter so high and volts clearly too low to charge the battery? Could the meter itself be sending a no charge to the computer or be causing it to not charge?

 

I would double check that fuse. From what I gather, if it is blown, the PCM cannot see the battery voltage, so it's cranking up the output of the alt (and reading high on the gauge). But with a bad fuse, you're just running off of the battery.

The trans shop may have shorted your starter wire or some other wire to ground, blowing that fuse, causing you a massive headache.

 

With a blown fuse no voltage will get to the battery. Check it with your meter (continuity).