I have a 1990 Cummins cannot keep a voltage regulator in it they will last for a couple of months, then will either short to ground or open up. It will either overcharge or not charge at all.  I have been getting them from Napa,. Anyone with any ideas,  help would be greatly appreciated.

I would have the alternator checked it might have a bad armature winding that is killing the voltage regulators. Basically, in a nutshell, the charging system has been the same for years. Blue wire is +12V key hot then the green wire is variable ground from the voltage regulator. So the blue wire supplied the sense voltage to the regulator and then the case would supply the ground for alternator as well as the alternator. So verify the green wire is not shorting to ground or opening up. Then verify the regulator case has a good clean ground contact. 

I have checked all cables, and ran aground from the battery to the case, I will have the alternator checked. Its simple the way it works but a regulator ever couple months is getting old.

 

Thanks for the reply I will have the alternator checked.

Run a dedicated ground from the VR to the firewall, assuming your existing battery/frame/body grounds are good.

 

Also check the ground from the alternator to the front of the block.

Edited October 29, 20186 yr by ofelas

13 minutes ago, ofelas said:

Run a dedicated ground from the VR to the firewall, assuming your existing battery/frame/body grounds are good.

 

Also check the ground from the alternator to the front of the block.

 

Running a ground to the chassis of the PCM will do nothing. None of the internal circuits ground to the case of the PCM. If using an external regulator I highly suggest you only use that is a temporary fix till the PCM is repaired. External regulators were discontinued because of charging problem based on its method of temperature detection. 

 

PCM ground is the actual passenger side battery terminal no added ground required.

 

If you want a good ground system look at W-T ground wire mod.

My simple version...

 

Edited October 29, 20186 yr by Mopar1973Man

Excellent info, but not applicable in the original posters case.

 

89-91.5 12v trucks used a grounded VR stock.

 

No PCM controlling the voltage regulation.

 

Running a ground to the chassis of the PCM will do nothing. None of the internal circuits ground to the case of the PCM. If using an external regulator I highly suggest you only use that is a temporary fix till the PCM is repaired. External regulators were discontinued because of charging problem based on its method of temperature detection. 

 

PCM ground is the actual passenger side battery terminal no added ground required.

 

 

Edited October 29, 20186 yr by ofelas

Opps. My bad... 

 

Got caught off guard by a first gen poster. 

First genners are real people too 

Thanks for the input guys,. I went to the dealership and go a regulator that was made in America.  They told me the $12.00 regulator is not for the diesel because of the high amp alternator.  I moved the regulator from the firewall to the fender well away from the heat of the exhaust manifold, which with the hood closed is about 3 inches away.  It seems to be working fine now.  It does have a two year warranty now which is a good thing.

1 hour ago, ofelas said:

First genners are real people too 

 

Rare to see them... Yes, they are real people too. But just as rare as Hen's Teeth or Rocking Horse Crap.

15 hours ago, Mopar1973Man said:

 

Rare to see them... Yes, they are real people too. But just as rare as Hen's Teeth or Rocking Horse Crap.

Not Dripley though.......        Sorry Dave couldn't help it  

Edited October 30, 20186 yr by JAG1

Forgot to get back to this issue.

 

Check AC ripple for a failing alternator diode, and use something like a Mopar Performance P4529794 VR.

 

Continuity & voltage drop checks on all existing cabling are a must before replacing hard parts.