Need a little help here guys. Okay, I bought a 1990 W250 pickup Saturday. Pretty nice truck. The guy had replaced the battery, cable ends, and alternator. I noticed he had also added a new regulator on the fender well. Didn't think much of it as it worked and this is a farm truck after all. Yesterday I get in it and it isn't charging. It was one of those cheap reman alternators and I have a 1993 parts truck so I yanked the alternator off and put it on. I hooked things back up and eliminated the external regulator since it was an internal regulator alternator. Started it up and it was charging like a champ. Came out of the poultry houses this afternoon and.......nothing. It's not charging anymore. So, where do I go frm here? Is this a wiring thing or does it have to do with the PCM? I can take the one of of the 93 if I need to. Thanks in advance.

Are you saying you took the alt of a 93 Dodge truck ? Because they dont have internal regulators. On the 93 truck the reg is in the PCM. Ron

That is what I meant. Sorry if it wasn't clear. If the regulator in the PCM is bad then why did it charge for a short time and then quit? If putting an external regulator setup on it would fix it I could do that, but most of the time the regulator would cause over charging instead of no charging wouldn't it?

the common fix is to add the external reg.

regulator will do it correctly if it has proper sensing voltage and ground. no over charging problems.
very simple circuits.

personally I like using the single field vr since they are electronic now.

one key on 12 volt source, one ground to the vr.
one field line from the vr to the alt, and ground the other line. doesn't matter which one.