I am sure this has probably been covered but I can't find it so here goes. I have a 2003 ram 2500 cummins that has 15 volts coming off the alternator. Diagnostics I have done. With the ignition on at the 2 pin connector at the alternator I am getting 0 volts on the source #1 pin (black and white) and 8 volts from the field control #2 pin (dark green). My PCM integrated power modules don't match the service manual. The C1 (blue) is the one powering the #2 pin but not sure about the #1 pin since it sits at 0 volts. It seems from the service manual that the integrated power module C6 (black) should be powering the #1 pin at the alternator, but I could be wrong. But what I am trying to figure out is can I bypass to the source #1 pin from the C1 pin 4 fused ingnition swith output run or a similar source to get power so the #1 source? Or is this a commonly known issue when the ecm internal voltage regulator fails and can I use the external voltage regulator thread to bypass the ecm voltage regulator? Or am I totally wrong in where the source power comes from and that it should read 12 volts with the ingnition on? The problem is my altornator is putting out 15 volts and overheated a battery. I have replaced both batteries and the positive cable between batteries since the terminal end looked bad. I cleaned all battery connections and grounds but the alternator is still putting out 15 volts but jumps down to high 13's then usually sits in high 14's for 10-20 seconds maybe then up over 15 then down to 13 and on and on.

 

Are you watching the dash gauge or a meter on the batteries? For as reliable as 3rd gen clusters are I would say things are just fine, maybe a gauge going bad. If voltage is actually jumping that much and you are confident in your batteries and cable connections, I would next check the power supply and ground quality to the PCM if its getting poor supply voltage it will command the alternator respectively. Lastly it would sound like the internal regulator is starting to go wacky. I'd check out a one wire conversion before jerking around with an external regulator

 

All readings are from a voltmeter not the dash. Dash voltage is not reading at all but was before this started. I may have left that out. I had a battery overheat this is what started it all. I'll check out the link you sent for the one wire conversion thanks. I do have voltage at pcm and cleaned all ground, but can't determine what pin supplied my alternator supply. My wiring doesn't match the service manual I was able to get a mentioned in my original post so can't figure out where to check to see if an internal module is faulty.

 

Which battery overheated, if its the passenger I would Definitely be 300% confident in my battery cables before going any further. When I rebuilt the cables in my 06 Cummins, I had the alternator extended to charge the drivers side battery to hopefully curb any future protentional problems. Make sure you keep the fusible link, don't just make a whole new cable.

 

It was the passenger side and I did replace the cable on that side going to the other battery. I did replace the fusible link with a new wire. So I need to go back to a fusible link. But would that cause the alternator to send 15v and fluctuate? I still get 0 Volts on the source pin and 8 and the field pin at the alternator 2 pin connector so there is something still going on. I haven't replaced any negative cables because they all looked good but I did clean them really well. The driver side positive cable is still old too but cleaned it really well. I could Roland that but still with 0 volts on the source pin at the alternator I think I have something else wrong. But I'm not 100% sure about the source versus the field pins at the alternator but based on the service manual generator connector diagram I'm correct. But from research it seems like i should have 1 pin at 0 volts and 1 at 12 volts at that 2 pin connector at the alternator with the ignition on. But I have 0 and 8 volts but on the opposite pins I think i should and low volts.

 

I just found this post and I am having the same problem, last week I over heated my passenger side battery. I replaced the alternator because I thought internal regulator must have went bad.(then I found out it's the ECM). I was reading 15.2 volts off of my tuner yesterday. This morning I started the truck to warm it up and my new battery overheated too. My question is, has anybody installed an external voltage regulator on a 2007 5.9 diesel or do I bite the bullet and get my ECM rebuilt. I am thinking if you can do it on a gas engine you should be able to do it on a diesel and it's a lot less money than a ECM. If someone has installed the external voltage regulator, can you let me know where you got it. I have new cables that I was already going to install this weekend so that part is covered at least.

 

As I have posted on other threads, I would thorughly test all connections before just assuming the regulator is the problem. The ECM/PCM needs to be seeing correct voltage and ground, then make sure the wiring is good from the PCM to the alternator. A bad connection between drivers and passenger batteries is a big issue. I would highly recommend installing a crossover cable from the alternator to the drivers battery, or atleast a jumper cable and re-test. If the regulator is absolute the fault, I would install a one wire alternator before jerking around with hooking up an external, most people can't setup one correctly.

 

I have new cables, just got them yesterday in fact, So clean and replace them and test the output first on both battery's? then maybe have my ECM repaired if it's putting out to much voltage then? I just read that the voltage is only read on the drivers side, so the passenger side could be way over voltage and you wouldn't even know it unless you tested the passenger side.

 

Correct, you need to test voltage on both batteries separately

 

Well I have not had a good month with my truck, I ended up ordering a rebuilt ECM because my second battery blew up 3 days after I replaced the alternator, cables and battery. ( I finally did a little research and found out the ECM controls the voltage now).
Got the ECM back, installed it and they didn't have the right VIN code entered into it.
After that, i got 5 codes
SRS Codes
U1415 Implausible/Missing Vehicle Configuration Data
ABS Codes
C2206 Vehicle Configuration Mismatch
C1079 Tone Wheel Teeth Count Range Performance
PCM Codes
P0480 Cooling Fan 1 Circuit /Open ( This one is due because the previous owner changed it to a mechanical fan)
U1412 Implausible Vehicle speed signal Received
So I shipped the ECM back for them to reprogram it with the proper VIN, got that back Saturday and reinstalled.
Now I have all the above codes plus 3 more under the PCM
P2509 ECM/ PCM Power signal input intermediate
P0483 Cooling Fan Speed ( Again probably because of the fan change)
P0633 SKIM Secret key not stored in PCM
I have tried everything I can think of to get these codes to clear but I am no computer programmer and it goes to the dealer tomorrow.
I would like your opinions as what is going on, before the battery blowing up I had no lights on my dash.
Now I have the ABS, SRS and Check engine light on, also my speedo and 4 wheel drive wont work.
I drove it Saturday and it is shifting, but the brakes almost feel like manual brakes now.
With all this happening all at once, is it possible that it just needs a complete reprograming so everything can play nice again?
I can't see all these modules going bad all of a sudden, am I wrong?
Again, any input would be great.