Help Help truck not charging

[budmann2002]

ok so i wasnt sure if this was the right place to post this but i am in dire need of some advice. present situation is that my gladi is sitting in my driveway and the alternator will not charge the truck. before i have a bunch of folks tell me to just go out and buy a new alternator i need to give some background on how it got this way.
a month ago i had to take my truck into the bodyshop because a big storm blew in and decided that my neighbors trampoline was better off sitting on top of my truck. so after a two week vacation at the bodyshop i finally get it back. this shop gave me my truck back with the driver side mirror sensor going off constantly. and the battery would only charge up to 13.9 maybe 14.0 if i was lucky. and after about 5 min of it running in my driveway it would drop in voltage output down to low 11 and even into high 10 and get ready to shut off. now mind you i put that truck in the shop with no electrical issues at all. it would charge and stay charged at a constant 14.4 all day long.
so i do need to back up a week before it went into the shop. i was planning on putting a 320 amp alternator on the truck. i had it and it was a relatively straightforward install. done plenty so it wasnt too bad. so this the system that went into the shop. however i did not know and i do now, that the upper wire from the altenator had to be installed on the N7 post. whereas i had it installed on the battery positive. and the original wiring to the N7 post. so that may have contributed to a dead battery.
once i had the truck back in my driveway, i decided to take out the AUX battery and connect the positive from it to the positive to the main. taped off the ground from the AUX. i did leave the sensor on the main ground plugged in. (not sure if that may have contributed to my situation now) so last night i get the truck back from the dealership because they refused to even open the hood on it stating that the bodyshop said i had an aftermarket alternator on it and didnt want the liability. so anyways i get it back and i start to bring all charging system back to stock minus the AUX battery. and now it will not even charge up to 11.6.
where should i start looking. could i have blown the fuse at the N7 or do i need to find someone that can throw a scanner on the truck and diagnose. i am positive that due to the lack of competence of this bodyshop, i got back a big steamy pile of crap that i am still paying on by the way. i just need for it to charge the battery and stay charging. and my 320 amp alt will be going back on the truck once we figure this issue out. thanks in advance for any advice.

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[ShadowsPapa]

the battery would only charge up to 13.9 maybe 14.0 if i was lucky. and after about 5 min of it running in my driveway it would drop in voltage output down to low 11 and even into high 10 and get ready to shut off. now mind you i put that truck in the shop with no electrical issues at all. it would charge and stay charged at a constant 14.4 all day long.
so i do need to back up a week before it went into the shop. i was planning on putting a 320 amp alternator on the truck. i had it and it was a relatively straightforward install.

320?? Why? Your wiring likely won't handle that because the top output of a Jeep alternator is 240 amps when equipped with tow package, etc.
It won't charge your battery any better or faster to have that massive output.

Did you ever even try to charge the batteries correctly with a battery charger, and reset the IBS and go from there?
13.9-14.0 volts is pretty normal if the batteries are about 2/3 charged and the ambient temperature is above 50 degrees.
Running a constant 14.4 "all day long" is indicative of a problem in itself. They aren't going to run that high unless there's a problem.
So you need to forget that "14.4 all day long" as that's not necessarily normal. In fact if the batteries are at or near 100% charge, you may see voltages of 12.6 when on the highway. These are supposed to vary. These aren't old-school regulated systems.
Normal is anywhere from about 12.6 to 15.0 and all points in between depending on the state of the batteries, etc.
You need to charge both batteries independently to make sure both not only take a charge, but end up 100% charged and alternators are not battery chargers - use a real battery charger.
While charging each battery, disconnect the IBS for at least 10-15 minutes.
Once the batteries are charged, put it all back together and check things from there.

and the battery would only charge up to 13.9 maybe 14.0

Sorry, I fail to see the issue with that, especially if they charged the batteries or the IBS and BCM and PCM decided it didn't need more than that.

Yes, you may have blow the high current fuse array. For one thing I'd have to look but I don't believe it will handle that amperage!
And I can't figure out why anyone needs anything over the 240 amp. A 320 is more bragging rights, unless you have MASSIVE old school non-LED lighting that would tax a 240.

I checked and was correct, that high current fuse will only handle 300 amps.
If I was you, I'd scrap the crazy alternator and put a 240 on it. So far I've not seen anyone complain it wasn't strong enough.
You can't run a larger alternator through that fuse array and not risk blowing it.
The wiring won't support it, and there's 0 need for it.

Frankly, I don't blame the dealership - I'd not touch that one without you signing off on paying them any diagnostic and repair fees.

i was planning on putting a 320 amp alternator on the truck. i had it and it was a relatively straightforward install. done plenty so it wasnt too bad.

You might want to go back and check the others.

Is the 320 made for a smart alternator system that's controlled by the ECU and not a dedicated voltage regulator?

You never wire an alternator directly to a battery without a fuse or fusible link - so do watch for that in any future installs.

Please don't blame the truck for your wanting a massive alternator it was never made to handle.
I wonder how the PCM might handle the rotor current through such a massive rotor/field winding.
We know the fuse array, which is ONE assembly for all of those fuses on the end of the PCM - replace on, you replace them all. It's only 300 amps.

 

[budmann2002]

ok, so i had to read this post several times before i made this comment. while i do understand you not understanding why i chose a 320 amp alternator. i have also read a lot of your other posts about batteries and how you are feel no need for anything other than what the factory has provided. so with that out of the way, let's continue. as i said in my original post. i currently have the stock alternator and it is the 240 amp model. so when i start the truck i can tell that it is not charging. when you say " We know the fuse array, which is ONE assembly for all of those fuses on the end of the PCM - replace on, you replace them all. It's only 300 amps " are you referring to replacing the entire fuse box array? i also stated that i am only running one main battery at the moment. i do not plan on returning AUX battery to its place. what i am looking for is a starting place to fix this charging system so that it works as it should. in its current state, it is not operating correctly. i will also take that consideration in hand about re-installing the bigger alternator. hell im game to try anything.

 

[budmann2002]

is this the fuse array you are referring to?

 

[sharpsicle]

A few questions I have reading all this.

1. How are you determining that it isn’t charging vs not needing to charge?
2. What’s the condition of the battery? Had it been tested?
3. Have you done any checking if the simple things, like fuses?
   

 

[ShadowsPapa]

is this the fuse array you are referring to?

Yes, that handles all high current devices, including the charging system (alternator to batteries)
If that's blown, any number of things can happen, including battery (batteries) not charging.
Make sure you get the right one as there were earlier versions that supported lower amperage for non-tow package JTs. They changed them sometime around 2021 model year I believe.
That is the high current fuse array - it's on the end of the PDC on the engine end where the studs are (where N1-N8 are)
Any one section blown, you replace the whole thing.

Did you pull fuse 42 (I think it's 42, I'd have to check my notes) when you disconnected the aux battery? Otherwise it's going to run a check, or try to, and open the PCR when you start it - causing an error if it doesn't see voltage when it does that. Pulling the PCR relay fuse ensures it can't open the PCR and it will see the voltage of the main battery and not have a fit.

Make sure the battery is fully charged and the IBS is reset since you've done so much with it, who knows where it stands - you need to start at ground 0.
Use an independent volt meter, not the one in the dash, and check battery voltage with it not running.
Then check with it running - outside volt meter, just to be sure.

I can't say how much current the ECU can handle as far as alternators - it's remotely possible that it's having a fit after trying to control the big current flow through the rotor of that bigger alternator. And going back won't resolve blown fuses or messed up control units.

I have an amp probe and scope I'd use to check the field current, pattern, voltage/current flow through the field to determine if the PCM is even trying to control it.
(I check and repair and restore charging systems, etc)

 

[Hootbro]

What a flipping mess. I would not even venture to give advice until everything was back to stock.

 

[budmann2002]

ok all is good now. i did put the battery on the charger last night for good measure and it needed it. i havent driven my truck in the past month. its been back and forth between shops. i did take off the 320 amp alt and put my stock unit back on. i replaced the fuse array, because it was indeed no good. after all was buttoned back up, i fired it up and it was charging like it should have. Oh and i did pull the 42 fuse just because you suggested it. the IBS had already been unplugged from my previous research before this post. thank you for all of your advice. but be a little more open minded about people wanting to add amplifiers and lights and what not to their vehicles. i have been doing stereo stuff since i got my first car. but this smart charging system was a first for me. lesson learned and onto to other things.

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