I'm not sure when my battery light popped up but i have to charge my batteries every 5 days.. I went on a drive to go ride Dirtbikes and on the way there I noticed my stereo would shut off at random and my volt gauge was all the way low. I got there, rode and had to jump the truck to start it to get home, the batteries did not charge and I ended up driving with no lights no stereo nothing. In the dark all the way home. Pretty scary

I figured it has to be the alternator, I checked my old one and it was 11.5v at idle so sweet bought a new one, installed it, started after cranking for a few seconds. Got 10.1v and this is directly off the alternator. I got a voltage regulator and after cranking a few seconds to start I got 9.5v now. I charged my batteries and I got 12.3v. At this point I believe it has to be my batteries right? But why would batteries make my alternator not put out the right voltage.

Again. I'm reading alternator voltage directly on the alternator

 

It's not something uncommon, and once the acid in the battery, and the plate break down enough, you won't be getting the charge you need. Also had it happen where mine was so worn down, it reversed the polarity of the terminals, was an adventure replacing every fuse/fuseable link

 

So just get some batteries and it will work? I'm hoping it was just some fuse and I didn't have to spend $400 on batteries

 

I would try batteries, since they have such a large draw on them with the glowplugs, and cranking over such a large engine, that they will fail quite easily

 

Bought new batteries and swapped alternator to a new one again and it's 12.4v

 

Glad to hear it, these lead batteries are only meant to last 2-4 years at the max (unless you know how to clean them and condition)

 

Okay... Getting 10v today off my third alternator. Suspecting something else there's no way my alternator could "go bad" then get two faulty alternators. I'm guessing the 12.4 I was getting was from my new batteries.

 

So you are still having this voltage issue again, or you tested the alt. out of the truck

 

Not yet

 

Voltage regulators are a major pain on these trucks .. i blow one every winter about a month into the cold season .... not really sure whay that seems to happen ... BUT its like clock work .. i keep a spare in glove box ...

Check the field wire from the regulator ( exciter wire ) and check the realy wire ( shold be giving the regulator the voltage @ batteries ) ..