So far I have been testing the main cable yes, also the leads of the fuse, which amounts to the same thing.

Heres old, and new.
Whats that little box circled, anyone know if theres anything that could fry in that. ?

 

Anyone know where these fusible links are supposed to be, and/or which wire supplies the field voltage ?

I'm only getting 12v at the battery, GEN light keeps popping on, so obviously I have a problem.

 

You best bet would be to get a Haynes. The diagrams are pretty good.

Don't get all upset, but, I think you are making this harder than need be. Have you tried disconnecting the pos. cable while the truck is running?

 

I have a Haynes, and am not upset.
Am looking for a few simple answers to what should be a simple problem, and am not finding them.
It will not fix itself, I have done everything I can think of, short of taking it out and having the new alternator tested and, if it tests good, which it should, I will then probably have to take it in for professional diagnosis as to why the charge is not getting to the battery.

Haynes has very little info about self diagnosing charging problems.
I am not getting proper voltage to the batt, so that pretty much limits the possibilities to the alt itself, or the wires/connection in between.
I have looked high and low and could find no fusible link, so I guess I'll yank the damn thing and have it load tested at a parts store.

 

what's your voltage at the alternator. 14v, 12v, or 0v.

what's your voltage at the battery.

i don't know if its a good idea to disconnect the battery on a modern/computer controlled vehicle while its running or not.... so i won't suggest it.

isn't the voltage regulator in the pcm? or not.

 

He said it's 12v, but I think he said he was going to charge the battery.

You can load test yourself actually. Start the truck, put the meter on the battery see what it says, now turn on the headlights. The volts should drop for a second, but should then rise as the alternator works. If it just keeps dropping I'd say the alt. is no good. And yes the voltage regulator is in the PCM (yeah, another great design) It's pretty rare that it fails though. Also, if you pull it to have it tested, you should take the battery too and have it tested as well.

 

Yanked it today, passed the bench test 3 times.
Battery is a new Diehard, which takes and holds a charge just fine.

So somewhere in the wiring apparently a little gremlin resides.

 

Had a pro come out today to check my charging problem, found him on craigslist - Came with a snap-on scan tool, 1st time I've even seen one of those.
He found out pretty quickly that the alt was trying to do its job, he rigged up something that made the voltage across the battery jump from 11 to 16 when running.
He verified the problem was not in the harness, but in the computer.

Bad news, but the good news is he said he could rig up an external voltage regulator that would basically do the computers job, and allow the regulated charge to go through, as normal.
Only downside, he said, is it will likely continually throw a code and/or the GEN light would stay on, but I can live with that rather than blowing a bundle on a new computer.

 

Bummer, atleast you know what's wrong now. By passing is ok, but now you won't know when the alternator goes out next time.

 

Well, if it goes out with a billow of smoke like the last one, I will !

I just don't see spending $200 when I can get this done for $50, same thing accomplished but yeah, could lead to headaches down the line.
Like they say, "just lookin to get through the winter"