Fired up the truck this morning to go to the tire shop for 4 new tires on the rear axle, got 1 mile down the road and the "check gauges" light lit up. Voltage low on instrument cluster. Thought maybe the 150amp breaker tripped in the charge lead. Nope, it was fine. Turned around and went back home. Pit a voltage meter to the stud on the back of the alternator and she read 12.8v. I guess it's time. Ugh!!!

 If it isn't one thing it's another! 

PCM protect fuse blow? 

Tach signal present to turn on the PCM?

Are you seeing voltage on the blue and green wires while the engine is running?

 Ugh, I'll be honest. I didn't check any of that and I never got the pcm protect fuse installed. I know the alternator was only putting out 12.5 volts, if that was output. It could have been battery voltage. No 14v present so I ordered up an alternator.  The truck is my daily and need it back. At the moment I'm stuck using my dad's mustang. Talk about 10lbs of taters in a 5lbs bag! Man those cars are small!

Better check everything. You can buy an alternator and slam it on and still be dead if the PCM is fried.

Is there a place nearby that can test the alternator before you buy another one?

 Not really, I'd have to drive 1/2 hour to get to a test bench. 

 New one should be here today.

 New alternator is now installed. She's alive!!!

 Removed the old one and spun the pulley and the bearings seem nice and smooth. Had a conversation with @Mopar1973Manyesterday, I think I will rebuild the original with new brushes and regulator, clean it up and stock it on the shelf for a spare. Never hurts to have apare parts!