I have a 1998 Twelve valve Cummins Turbo, 3500 Ram, 4x4 Auto trans.

I think the PCM is down, and I have heard some folks have wired in a voltage regulator

My truck has been down for about 5 days now- and I need to get it moving- the altenator is puting out, but no charging at the battery, and I understand that some folks here have wired in an older style voltage regulator- anyone have details on this? -

Anyone know which voltage regulator to buy?

I am immobile right now, and my mopar is my only form of transportation for my family!

 

Tach working?

 

Yes, tach and all guages work- everything electrical works EXCEPT for charging. Grrr.

 

What do you mean the alternater is putting out? Have you checked the alt fuse in the PDC? What voltage do you read across the alt field windings? What voltage at the battery when running? Check connections to battery, alt and gnds? You could have a bad alternator.

 

I ran all the voltmeter diagnosed stuff- straight out of the FSM, including running with all accesories on at 2200rpm.

Altenator was bad, was replaced, now good. Still no charg-y Charge-y.

 

I ran all the voltmeter diagnosed stuff- straight out of the FSM, including running with all accesories on at 2200rpm.

Altenator was bad, was replaced, now good. Still no charg-y Charge-y.

 

Humor me!
The two small wires connected to alternator.
One is battery voltage when running.
The other is field control through the PCM.
Take a 5 amp fused wire and ground the field control wire for a few seconds.
Alt out put should hit max. You should hit 15 volts at battery.
If you don't. The alt is bad. The bat wire is bad. The voltage supply to field is not functional. The belt is slipping. You figure.
If it does charge. The wire from alt to PCM is bad. The PCM is bad. You missed something in wiring check.
charge-y Charge-y

 

I will try that first thing tomorow- thanks for the tip!

 

Okay- no voltage to battery. Maybe alt bad? Will take it back and exchange it- it may very well be bad.

 

The entire situation sucks. I gotta have some fault in the wiring harness, even though I show continuity to everything. Something sucks. I can't even jump the battery direct from the altenator.

 

Take to Alt/starter shop and be done with it. Hope you're better at bending metal than figuring electrons.

 

No **** huh? Ya, this one has me stymied- I have found one, and one only, place that actually might be better than this than the guys I have brought over and myself- but it is my last resort, it may be more expensive than just me go replacing stuff!

Will get the quote next week, see what happens.

I may have also just picked up a 92 Ramcharger in perfect shape (body and interior) and no engine- if so, I will be looking for a 4BT!

 

Huh?....I don't understand what you're doing! This can't be that tough to figure out. What results did you get with the tests from "CruisingRam" here:If the alt is not charging the battery than follow "CruisingRam" advice and you should find your problem. You understand that the PCM is the regulator for the ALt. The ALT does not have an internal regulator. The voltage on the wires going to ALT field from PCM should tell you the PCM is functioning (or not) and also the ALT is responding (or not) to the PCM request for more charge. The rest is just wiring.

I guess I'm having a problem understanding just what your results are and what tests you have done to arrive at your conclusions. Be real specific on what you do and the results. Sorry for all your grief over this. Without us there we need detailed info to help.

Good luck,
Dave

 

Got everyone scratching thier heads on this one bro- I wish you were here, quite frankly- got a new alt- brand new- this is the second, they warrantied the first- did the "hot field" jump to the battery- okay- no chargy- so that means- well, must be a ground fault SOMEWHERE- right? I went through entire test procedures, printed off everything here and on two other dodge truck sites- had competant wiring guys here, thought for sure, that if it were a "edit" on my part- you know, like proofreading my mistakes or something. It is a "ghost" problem or something- we tried the voltage regulator thing- and, in fact, my bro, who is a licensed cummins mechanic, got the same bulletin on the voltage regulator swap- still no worky!

Only thing we can think of- there has to be a wire fault somewhere between the altenator and the batteries- right?

I mean, ****- I have NEVER seen anything like this before.


Here:If you don't. The alt is bad. The bat wire is bad. The voltage supply to field is not functional. The belt is slipping. You figure.
If it does charge. The wire from alt to PCM is bad. The PCM is bad. You missed something in wiring check.

Only two alternatives as far as I can tell are in bold?

 

Tough trouble. If voltage from PCM for field windings is not correct than either PCM is bad or wiring.

Reading thru my 97 manual the PCM controls the output to the ALT field windings using the output of the "Battery temperature Senser" located under the drivers side battery tray. What if its bad? Maybe iits given the PCM an incorrect reading so the PCM will not supply the correct charge to the ALT field windings. The drivers side battery has to be removed to get to it. Just a thought. If your not getting codes than its likey good.

Also, there is a note in my manual stating that there a different generators used with different output ratings so be sure to get the correct one.

Also the field winding relys on a good ground that goes to the alt. Make sure the GND is good. Try using a jumper cable from that gnd to engine/chassis.

There is a big red battery cable connected to the generator. If you read 12v with truck not running then that connection is good. If bad then check the BIG 120 amp ALT fuse in the PDC on drivers fender.

The 2 field windings are both connected to the PCM. One is the PCM "Generator Output" and the other is the PCM "Generator field driver" which goes to gnd. I'd be verifying that all these connections are good from PCM to ALT.

This is obvious but did you have your batteries tested? If not then charge then and then take them to have them tested. Maybe you already have done this but start with good batteries.