I've been thinking about the PCM Field control test by CruisingRam. The field windings should be marked (-) and (+). If think that (-) wire (Field control...make sure its not the field winding that should have 12v or battery voltage on it) goes to PCM. PCM provides a "current" (Amps) control of charging current for alt which is to thru the PCM to ground. So the Field Driver (Control) side of the field winding to the PCM is on the low voltage side (-)of the field winding. Make sure this is the (-) field winding not the (=) winding for the Fused GND test of the Field Contrl winding.

By attaching a 5amp fuse to GND momentarily (at the - Field Driver Control winding at the ALT) and at the same time that you are grounding this wire you are watching the battery voltage at the battery (or the BIG red battery lead on the alt) to see if it reaches it's max voltage, then you are proving that the alternator can indeed supply the 15 v(MAX). In other words you are becoming the regulator function normally supplied by PCM. If alt responds with upping the battery voltage than the alt is good.

Correct me if I'm wrong. I assume you still keep all the field winding wires connected for this brief test. I'm not sure of the other field winding (which is the + winding) and how it gets 12v since it appears to be connected to the PCM also.

My manual shows this test and mentions that the + field terminal will show battery voltage (12.5-14.5 v) and the - field terminal will show 3-5 volts less than battery voltage on the + field terminal. It also says this test thows a DTC code and also if you ground the + terminal by mistake "Damage to electrical system components may result". Also do not do test more than 15 sec. They are using a load of a carbon pile rehostat on the electrical system to prevent high current. We are not so do the test briefly. If this test gives the max output voltage then the ALT is OK and may be bad PCM or connections.

Are you sure you performed this test correctly?

 

I have had two more than competant electragicians re-run my tests- all come up the same.

Here is my newest quandry- go to the last electrical specialist shop I can trust in Anchorage- tell him to go for two hours, if nothing can be found for certain- then button it up and stop.

OR- I can spend about 550 bucks on a new/used wiring harness and PCM.

What would you do?

 

I'll try again.
Don't believe you have said whether you can make alt charge by grounding negative field control with fused ground? Voltmeter at large terminal of Alt.
I assume you have charged batteries and engine runs from the jest of your thread.
What is voltage at batteries with engine running?
What is voltage at batteries with engine running, with headlights on and heater fan on high?
What are you using to confirm not charging?
You said: running jumper wire from alt (large term) to a battery and still did not charge. Is that correct? How do you know not charging?
What is your test instrument? What manual are you using?

I'm trying to make sense from your statements. Diagnois by committee and jumping around will not fix your porblem. Seriouslly doubt you need wiring harness and bunch of parts.

 

I would hook up an external regulator. Simple and costs less than $20.
Any 12 volt regulator will work. Just disconnect the two small wires from the alt, tape them apart so they don't short. Follow the picture below, two wires to the alt are interchangeable.
Many folks have done this, some claim the external regulators do a better job than the PCM.

 

Tried it- no chargy- that is what keeps me going "it has to be a broken wire somewhere- but where?

Checked batteries with a load tester- batteries great

Voltage at batteries is around 11-12 volts, remains the same no matter what I do- no chargy

drops a bit with everything on, like to around 10, depending on how long the batteries have been on the trickle charger

Voltmeter- tested it on working car, everything just fine

And on and on.

 

O'k you're doing good. Now for some futher testing.
Test for continunity from alt Pos (Big terminal on alt) to battery positive POST. Find something to make at load on the battery. A headlight bulb, a 12v electric motor or ideally a carbon pile load tester.
With engine not running hook the load to big alt terminal and ground very near or on the alternator housing. The light should burn or motor run since you have a direct path from bat pos to alt pos. You said the 140 amp fuse was good, remember.
With load still hooked up (and engine not running), connect the voltmeter pos to the bat pos. Now hook the neg v-meter lead to alt pos terminal. You should have the voltmeter on a very low v scale, like zero to 20 volts or less. If you read 10-12 volts the wire from alt to bat is broken. If light is dim and you read 2-8 volts or so, you have extermelly high resistance on this large wire. If you read .1 (one tenth) volts or less the wire from alt to bat is good.
Now check the ground side. Measure from the negative side of HL bulb to a battery negative POST. You should read .05 volts or less meaning you have a very good ground from alt case to negative POST. High voltage drop means bad connection/wiring.
At this time you have checked the power and ground circuits to alt.
Don't guess the answers, you have been two weeks already and not fixed.

 

Thanks- it will be done first thing in the AM oh jedi master of electricity ( and I am not joking- I am thinking electricity is some kind of fabled magic at this time, and my spirits are quite low!)

 

REPLACE THE CRANKSHAFT SPEED SENSOR !!

$109 from NAPA !!

I went thru this NIGHTMARE a few months ago myself!! My truck was down for weeks!!

READ (5 pages worth!) ALL ABOUT IT....

https://www.dieseltruckresource.com/...d.php?t=186943

The CSS shorted internally to the 5 Volt input source (back to the PCM) and caused totally HAVOC throughout my truck's electrical system. Including LOSING the source signal (EXCITER) to the alternator therefor preventing it from charging.


"IF" perhaps it does turn out to be your ECM, I have an EXTRA one here for a 98 12 Valver!! $150.

I never needed it after I installed the new Crankshaft Speed Sensor!

Email me if you need it..... Katmandu@woh.rr.com

 

You guys have been great- I am pretty sure that the cps is not out- as the tach works still, as does all my gauges- but I may very well take you up on the ECM.

Here is the plan- my brother, a licensed Cummins mechanic and one of the best mechanics on the planet, my best friend that works in the parts department of the local chyrsler dealer, and one of the best mechanics, second only to my brother, that was a mechanic out of his own shop for years (until he body was just too beat up, unfortunately) and his brother, who is the chief electragician at chrysler- I am setting them all up to come over on monday, and making it a bit of a small party. Beer and sandwiches and such.

I am printing off this thread, and any other helpful advice I find, and am going to attack this thing like the angry fist of gawd!

 

Roger that.

Let me know. Katmandu@woh.rr.com

 

Okay- I have printed off all the help, and my brother and I are re-reading them and re-reading them. He is the smart one, I am the not so smart one on this stuff- so this question came up-

Do you guys all have the same altenator as me? My altenator has a molded connector with five ( I think, or four) black connectors, and then two small poles where I think the green and blue small wires are connected too-

You guys are using the stock altenator to do the old voltage regulator?

 

I don't understand your description? Look at someone else's diesel. I believe it has a Denso or possiblly a Bosch. Can you by chance send a picture if not a orginal alternator. Din't you put a alternator on. The replacement would have been difficult to secure if not a orginal alternator. The parts store would have been stumped.

 

Okay- got the retro-voltage regulator to work- there WAS a break in that harness as well as the PCM being bad, as far as we can tell. I need to find an old plug for that voltage regulator so I can make sure it is firmly in place for long term use.

I will start a thread on looking for that connector on every mopar board I can find now!

Thanks guys- problem solved!

 

Are you sure that with the wire repaired, that PCM won't make alternator charge now. Suspect there will be some issues with ext regulator on fault codes. Aftermarket regulators are typically not temperature compensated and do not have good RFI protection. Get the genuine Chrysler regulator.
The VR plug you're looking for is avaliable at some parts stores, but a junk yard would be faster for me.

 

Doing this will not clear the 41 code will it?