Interesting stuff. I have the two inch sunpro gauges on my start kart, with both.. volts and amps. When I just turn the switch, it reads about 12.5 volts. When I start the engine, it reads about 13.5. The ammeter shows a slight charge. This is with 12v one wire alternator and 12v system.
So my question would be, does the throw of the gauge allow you to see the difference of about a volt and a half or two? What happens when you turn on the heater motor or electric wipers? If I were not looking directly at the gauge I have, I wouldn't see the difference. Has AMmeter technology improved over the years so it makes sense to put a more modern ammeter in?
I still come back to the fact that a almost totally dead battery shows 12.4 volts. So if you want to see what you are going to get after doing the mod before going to the trouble, buy the sunpro gauge that is called out in the procedure, put a cigarette lighter adapter on it, and drive your truck around with the dongle and see what you think.
