CruisingRam

I have a 98 12v Dually 4x4, auto trans. My charging system has stopped charging, and I am taking it into cummins northwest for an electrical diagnostic first thing in the AM.

I have a feeling it is the ECM and not the Altenator- partially because the tach is still working, and that is driven on the back of the altenator, correct?

So I am starting to price shop for both, and am really hurting for $ right now as it is, much less with a truck repair bill on its way- I have the FSM for this truck, and can do the R&R myself, but I am worried about parts cost!

Beat93

did you check the fuses? if its fine pull the altinator off your self and take it to a shop to test it. i know canadian tire in canada tests them for free. theres gotta be a place in the states that does also.

my computer or crank position sensor is shot in my truck so nothing works, no tach, speedo, chargeing system. so i wired up an external regulator to an on off switch for the altinator so i can still drive it around. there a diagram for it in the search, but i doubt thats your problem since your tach still works?

heykw

The tach runs off of the CPS

dozer12216

Have the alt bench tested. Very unlikely a ecm is bad. Test on vehcile has been somewhat unreliable.

heykw

I agree with the above

John Faughn

The best place to test is on the truck , will help to find the problem , with less work , the vast majority of charging problems are wiring / connections , the least likely problem is the computer .
4 wires on back / side of alt , large -batt. pos. , medium at mount - ground , one of the small wires to stud is key pos. , 2nd small is the ground side of the field to computer [ the computer puts a varying ground to this wire depending on everything els working & the need for charge / load ] this is the one wire you want to disconnect to do a in truck test [ a complete test , requires a amp meter that goes to at least 150 amps ] just because the volts go up , does not mean that the alt is good .
With that wire disconnected [ and the end of wire insulated /covered ] take an other jumper wire and touch that stud to ground with truck running & some one watching gauge on dash , this full fields the alt [ max charge ] so just for a few seconds .
Remember that those other wires have to have good connections ground , battery , and that the fuses , fuseable links have to be good /tested .
Many forget that the charging system is on of the things that go through the ASR , auto shut down relay .
Its late , but the 1st test is to with the eng. running , tap on alt with a screw driver handle , while someone is watching gauge , if it jumps up / reacts , you may just need brushes .
I also forgot , brand new , not rebuilt , Nipendenso alt , at this site .
http://www.fostertruck.com/dodge/default.htm

24valvepuller

PCM tells the Alt. to charge, when my alt. died it killed that part of the PCM, I have since had a shop put a regulator inside the Alt. and now have a power wire run to a switch in the cab, or you could run it to a keyed component but remember it takes alot of juice. It's either that or a new PCM

CruisingRam

Well, I did the tests- the altenator was dead- PCM fine. I also had the altenator bench tested-as well as the under the hood per the FSM that I have.

Changed the altenator, still no-chargy-chargy. PCM saying "give me fourteen volts" Altenator saying "I am making lots and lots of volts, no where to send it?"

I think the field wires on the back of the altenator, the little black box back there, has something wrong with it-

any way to test this conclusively?

John Faughn

You need to give more info , box , take a picture , I am not familiar with a box on back .
Your statement about lots of volts is off , there are only a few volts , 13-16 , charging is all about amps & lots of them 120 amps , with out a load tester & someone that knows how to read/use them , a good diagnose is hard .
You need to chase down the connections , the problem with dodge is that they go out of there way to make it BS , reg. in computer , auto shut down relay [ look at that ] and too many fuses .

CruisingRam

Okay- my altenator is making around 200 volts! I will take a pic as soon as I get home tonight and post it!

Thanks for your help.

CruisingRam

Well, no one in this town seems to know **** about the wiring on this truck. I am getting mass output at the altenator- but nothing at the battery.

I am about ready to try the altenator/wiring in an older voltage regulator like suggested before- anyone know which voltage regulator is used and have an idea what wires go where?

I checked further into that black wiring loom portion of the wiring- and it is nothing more than a molded plug- I was hoping it was some kind of fusable link- the FSM is pretty silent about all of this.

I think it IS one portion of the ECM (or PCM or whatever) that is dead- from what I can figure out, there is a positive readout on the PCM, and a negative reading at the PCM, and only one of them is working, and the diagnostic computer at Chrysler is not showing it, or the guy is not putting looking at the right data on the diagnostic deal-y.

I don't have the money to screw with this- and I am going to go in and ***** at Cummins for not doing what I said in the first place, and want my money back. Dude told me "there is no PCM on a non-EFI truck".

I believed him too- until I found the **** thing on the firewell. Just like the parts microfiche said looks wise.

dslpower

If you are getting a correct reading of 200 volts on the output of the alt, the Diodes are bad. Or you have an aftermarket one that makes 110 volts a/c as well as 12-16v dc.

Check the ground between the cast alternator housing and the battery Negative post with the meter set to OHMS or "beep" mode if it has it. If the reading is high or meter does not beep then alt has no ground.

Check alt output terminal with engine off-- should have 12-13v present. If no or low volts, then output wire to batt + is bad-burnt- fuse blown.

CruisingRam

The ingition wire side takes alot of juice? How big of a fuse is on yours that they take this wire off of? I ran mine off the blow motor circuit, 40amp fuse,

24valvepuller

Mine has no fuse, I ran a wire back inside the cab and hooked it to a switch that goes straight to the battery. I don't like to hook into other circuts with something that draws that much, when you flip the switch you can hear the truck load down like when the grid heaters come on. Might not be the best setup but it is on my pulling truck and as we are speaking the PCM and ECM are becoming door stops, all important guages will be mechanical

dozer12216

Run a wire directly from the big terminal on alternator to the positive terminal on a battery. You have a charging connection for sure now. You must be reading volt meter wrong. Cold day in you know where to get 200 volts on alternator.
Better yet take to alt/starter shop and get yourself out of trouble. Surely there is someone in Anck. that can fix this easily.