If your interested when i get out of the oilfield and get home i can show you how to make it work with the 3g swap, mine goes almost to the full discharge side then slowly comes back as the glow plugs warm up, then shoots back over to the charge side when started, slowly coming back to little charge as the batteries recover, just like it should.
Did you just install a new shunt?
I'm very interested. I'd love to have both. If my ammeter worked I'd leave the old one in there and put a voltmeter on my a-pillar.