thanks for posting this diagram. looked at a wiring schematic just now.
seems i need to modify my wiring some.
right now the alt output goes to the b+ on the relay, then i have a 10g wire that goes from the b+ to the A20A-10BK inside the cab, there is a splice somewhere in there that goes to the headlights and something else, then it goes to the ammeter. Then, the other side of the ammeter is original so it is the same as the S1-10-RE in the diagram, so it goes back to the B+ on the starter relay. both connections being at the B+ on the starter relay is going to cause it to be inaccurate right?
I started my truck this morning to have a look at the gauge once again, the starter makes the gauge show 15a discharge, then at a slightly high idle it shows about zero, if i rev it up some, it shows a few amps on the charge side.
Like i said before, at a low idle, voltage at the battery was about 12.8v and if I revved it up some it was about 13.3v.
It sounds like your truck's ammeter has an internal shunt.
Because it sounds like it originally had a heavy wire from the fusible link all the way to the ammeter, and a heavy wire from alternator output to a splice or splices with a brank to the other side of the ammeter.
A remote shunt would have small 18 or 20 gage wires going to the meter.
Using that diagram is probably not the best if the rig had an internally shunted ammeter.
From what you've described maybe something like the first one below.
The second one is typical '73 car. I dont have truck diagrams so can't help with that. That motorhome one the guy drew is the only thing I've seen.
15 amps discharge while starting is huge.
The question is why is any current going through the ammeter when you have it wired this way.
As far as the voltage goes, its not very informative. Could be anything from blown diodes to a short sucking power from the alternator.
I think you're best off wiring it up like the factory (using new connectorsand a grommet instead of going through the melted ones).
Then hunt for shorts with battery discnnected, or live, using a circuit breaker where the fusible link(s) goes.
