I'm wondering because I have a 100 amp alternator and an amp gauge staring me in the face that matches my other gauges. Is it less usefull than a volt gauge? I know I know, lots of power going to the dash area, but beyond that is a volt gauge really more useful? Thanks guys
I'm running a dual-field 1970's alternator (40-60 amps?) in a '54 Dodge pickup with the stock ammeter. I have heavy-duty wiring (I think it's 4 ga) from the alternator's output, thru a fuse, to the alternator, and the starter. I don't know how well a 50A gage will tolerate a big load, like a 80-100A. Of course, I guess the real question is how much electrical load will you run, and how low will you let the battery get? On my truck, all the loads in the car come off a terminal that's tied to the alternator output and one side of the ammeter. The other side of the ammeter is fed by the battery, via a wire from the starter where the positive cable goes on. So, when the engine is off, all juice comes from the battery, thru the alternator, and runs whatever loads are switched on. With the engine running, the alternator powers all circuits, and will push any excess back thru the ammeter until the battery's voltage comes up to match the alternator's output voltage. I haven't seen the charge gage move more than about 20A from center one way or the other, and that's not for long. Within a minute, it's always right near zero. So, I'd guess that I could probably have a 50000A alternator and it proably wouldn't make any difference; I don't sit with all the lights and accessories on, or run the battery so low that it takes a giant charge. If it were my project, I wouldn't worry about it. Of course, I have found that I should have worried a little more before... Edit: an ammeter is useful; a voltmeter is useful. Either is good. If I were starting from scratch, I'd run a voltmeter, since it doesn't require a big cable running all your power thru one gage - if a voltmeter quits, it won't stop the car. An ammeter could. But, if I am using an existing gage setup, I wouldn't change. -Bill
Thank you for your time to write that explanation for me, bill! I know answers take longer to type up than it looks, at least when I'm typing ;-) I am wiring from scratch, I think I'll toss that amp gauge on the sell pile and get a voltmeter, they're cheap enough and at least I understand what its telling me. Thanks again!
Why not buy a volt meter, make a print out of your amp gauge face and cover the face of your volt meter with the print out? Then your gauges still match and you have a volt meter that looks like an amp. If you got creative, you could even line up the "0" line right at where it stats charging.
Why can't you just wire the amp gauge to work as a voltmeter? Pretty sure I've read that's how you did it back in the day before you could go buy a voltmeter from 1-800-hot-rod.
When I got my gauges retrofitted from 6v to 12v, I had them (redline gauge works) put in a voltmeter instead. Looks the same but works differently. You need to run all your accessories through your ammeter to measure amperage draw, which some consider not as safe as a voltmeter. It could also be considered a single point of failure - if it fails so does everything else running through it - not so with a voltmeter. Interesting article: http://www.egauges.com/ATM_Tips.asp?TipPage=voltmeterammeter.htm
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