Join Date: Dec 2013
Location: Monterey, California
Ferrari Life Posts: 124
A voltmeter measures voltage, not amperage. Doesn't matter what the output amperage is so long as the correct range for voltage is selected on the meter. In a 12 volt system (actually charges up to nearly 14 volts, with the alternator output being a bit higher) set the meter range at 20 volts.
I'm about to switch the clock in my 328 GTS for a voltmeter (a Veglia model that matches the rest of the instruments) as I wear a wristwatch, but the car has no voltmeter, originally...I don't know why, it's very useful to keep track of the electrical system! I know this thread is pretty old but someone might read the last response and assume that voltmeters can't be used (???). As for testing a battery's output amperage, in order to be able to withstand a fair amount of amperage, rather than have very heavy wiring in the meter (which would make it very large!) car ammeters have "shunts" that only run a small amount of current thru the meter itself, rather than taking the full output. The meter is calibrated to give the actual output of the system or battery. So if a car ammeter is used, make sure it has an internal shunt, rather than an external one as some older versions used. New ammeters sold at auto parts stores have wiring diagrams to indicate which design the meter is. In any event setting up an ammeter can be tricky; voltmeters are much easier, the only caveat being make sure a wired-in voltmeter is wired to an ignition-keyed circuit, or else if wired directly to the battery it'll always give a reading, even with the ignition off, and will eventually drain the battery.
Last edited by Rich S; 02-06-2014 at 08:51 AM.