Quick question. The instructions say to ground it by going through the firewall and using a "good engine ground". For positive, it says to use the ignition switch or other 12V source. My other AutoMeter gauges are grounded to the dash frame and I'd like to think I can do the same for the volt meter. My real question is about the 12v connection. Rather than pick a switched source under the dash, wouldn't I have a better result tapping into the charging circuit directly by connecting it to either the starter relay stud or the alternator stud? Is there a reason why I couldn't use the red wire ammeter stud in the gauge cluster? I mean, the ammeter is a flow-through gauge and is directly on the charging circuit, right? Or does it not matter and grabbing a spot on the fuse box for example is just fine?
The starter relay stud, the alternator stud and the ammeter stud are hot all the time so hooking a voltmeter to them will discharge the battery over time...you want the voltmeter to be hooked to a switched 12V source.
I ended up connecting it to a switched spot on the fuse box.