Tripac Evolution software update?

Your alternator should produce at least 13.5 volts.
My truck and the apu each put out 14 volts.

 

I just put a new alternator in my truck. Old one was reading 12.5 volts. If my new alternator was putting out 12.5v, I would return it for a newer alternator under warranty.

 

The system voltage shown is the voltage being read from the battery, not the voltage output from the APU alternator. The negative charge current indicates the APU alternator isn't charging at all so there is no voltage from it. Don't return the new alternator just yet.

There is a post on the alternator that has two smaller wires connected to it. One of those wires is the signal wire from the control unit telling the alternator to start charging. I recently had the exact symptoms you are having. It was with an alternator that had just been replaced a week earlier. Turns out one of those wires was broken. Makes me wonder if the old alternator wasn't bad after all, even though the wire didn't seem to be broken at the time. Expensive mistake if so.