I am sure that I need a PCM.
Tonight i spent a couple of hours checking everything i could see.
the only thing that i found was a drop in voltage to the crank shaft sensor.
When the alternator was charging i had
5 volts on the first leg.
9 volts on the second leg.
0 volts on the third leg.
When i ohmed the first and third leg i showed 1500 ohms.

i reattached the sensor the alternator stoped charging after 20 minutes or so.
disconnected the sensor tested the voltage and ohms.
5 volts on the first leg.
3 volts on the second leg
0 volts on the third leg.
1980 ohms on the first and third leg.

So i am thinking that i need a new PCM.
I think the Dodge part#56026860.
i found this number on the PCM.
if anyone has any advice where to get a PCM or is there something else i should check i would sure appreciate any help.

Thank you

 

sounds more like a VR, what year is your truck

please update your sig.

 

This is going to sound stupid but what is a VR
My truck is a 1993 D250 2 wheel drive.

 

Vr=voltage regulator. This does not really apply as it is in the pcm. Sounds like you are on the right track.

 

today i installed a exterior voltage regulator. the alt is charging great only problem i have now is that the ac compressor will not turn on.
anyone have any suggestion on what to do next.

 

Check and make sure it is plugged in by the alternator, may have gotten unplugged while doing all of the testing.

 

yeah unfortunatly it is plugeg in.
i installed the vr next to the relays. conected vr to all factory wiring,
i spliced into wiring by pcm. wire nuted the wires comming out of the pcm.
im glad winter is setting in, dont need ac till april.

 

The A/C won't work because the PCM does not know the engine is running. You have a crank speed sensor problem, not a voltage regulator problem. Check the wiring to the crank sensor and the gap between the sensor and the damper.

 

I've got the exact same symptoms. After 20 to 30 minutes of driving the volt gauge comes up to normal and the A/C will work. Any way to check the crank sensor?

 

Tonight i disconected the exterior voltage regulator.
i took my truck to the store the truck would not turn off had to disonnect the vr and then had to remove the neg bat cable to get the truck to turn off.
so i connected the alt back to the pcm.
what is the gap setting on the crank shaft sensor. i am going to get a new sensor this weekend.
the tech at dodge was telling me that if the sensor is bad it shouldnt work at all. but this charging issue is intermitten.
thanks for everyones help.

 

The gap should be 0.050". A little tight is better than loose.

Chafed wires, a corroded connector, or loose sensor mounting bolts (allowing the gap to change) are much more common problems than a bad sensor.

Also try swapping out the ASD relay with the A/C relay. A bad ASD relay (or just a bad connection there) will cause a no-charge complaint.

 

Anyone has an idea were to get a crank shaft sensor online would appreciate any help, dealer wants $140 i think that is to much $$$$$$$$$$$$.

 

Well now I need help.
I went to my local dodge dealer to get the crankshaft sensor for my truck.
The dealership quoted me $108.00 for it and they would need to order it.
I went there to pay for it.
I asked to see a picture of it, they showed it to me it wasnt even close to the one in my truck.
come to find out they were looking up a sensor that was for a gas engine.
They cant find the crankshaft sensor for my truck.
They dont even show one in there system.
So the help i need is a dodge part number if anyone has one.
Thanks.

 

I wasn't able to find one, but guys seem to have better luck (and lower pricing) getting the crank sensor through Cummins.

 

Wannadiesel you were right it was the crankshaft sensor and you were also right on the money when you said to try Cummins for the sensor.
I went to Cummins on monday and ordered the sensor had shipped to the house arrived today installed in the truck. Now it is running great. Charging correctly.
Wannadiesel thanks for your help.
Local Dodge Dealer wanted $139.00
Local Cummins Dealer $60.21
Part# 3924432 Speed Sensor (Crankshaft Sensor)
I want to thank everyone for there help. I was starting to pull my hair out over this...