I understand what you are saying, but look at my example. If you were to change the resistance of the shunt wire you will affect a change in the meter, meanwhile the voltage drop stays the same, at 12 volts.

Just because the ammeter is on a shunt does not mean that it is suddenly a glorified volt meter.

Ultimately it's not worth fighting over. There are pro's and con's to each, which is exactly why whenever I can afford to do my aftermarket gauges, one of them will be a voltmeter. Having both gives a complete picture, whereas having either one only gives part of the story and we can both argue the point until we're blue in the face and to what end? Seeing who can get bluer?

Your truck just came with an idiot light, to which case it is much easier, and much more practical to put in a voltmeter, so put in a voltmeter! It is hardly practical to install an ammeter aftermarket! For those of us who do have ammeters, however, it is important that we understand enough about the system so that they read correctly, and that is what the original poster intended. He knew that the way his accessories were connected was causing his meter to give him a false charge, which made it wholly useless and wanted to correct that. He knew the answer already, just wanted to verify it.

We're all here to help, not fight right?

For some reason I can't get the image of Bugs Bunny and Daffy Duck arguing over it's duck season or rabbit season out of my head.