hi sl6 sages- wondering why you rarely see an ammeter in a car sl6 or otherwise, but always see a voltmeter or voltage triggered idiot light.. know that volts are electrical pressure and that a typical gas car needs a charging system putting out 12.5 to 14 volts to keep the battery up. you can check that easily by putting the two probes from a voltmeter across the battery terminals at idle. i have seen a few old tankers from the late 40s, early 50s which had ammeters- listed as amps on the dash gauge. this may be because, pre 1956 american cars were usually 6 voltpositive ground . the 6 volt batteries had higher amperages than later 12 volt negative ground cars. this is why 6 volt cars had heavier gauge battery cables . hooking up a meter to check amps isa little more involved requiring at least a 3d wire to the field of the chargingsystem.. know that amperes refer to the amount of electrical energy or power in a battery. sages used to say buy a battery which has cold cranking amps capacity at least equal to the cubic inches of your engine.never saw a post 1956american car with an ammeter unless someone added it from the aftermarket. not sure what useful info the ammeter would provide in a dailly driver manufactured in the last 50 years. can any electrical sage in the forum shed some light on this question. feel free to correct any erroneous point i have made. wont bore you with any obtuse responses i have heard in the past. i suspect falling amperage would indicate a battery losing or failing tohold its capacity, but wouldnt falling voltage show the same weakness and therefore having two gauges would merely be redundant. thanks bob

Ummmmm...because you need a new eyeglasses prescription? Most Chrysler products had ammeters for decades until voltmeters began to be phased in starting in the mid-late '80s. All the '60s-'70s cars with slant-6s have an ammeter as factory equipment. Many of the post-'76 ammeters (w/external shunt) don't work very well or last very long, but that's a separate question.
Can't think of many/any slant-6 cars factory equipped with either a voltmeter or a charging system idiot light.
12.5 will drain the battery. A fully-charged "12 volt" automotive battery has an actual voltage of 12.8 volts. The charging voltage must be above 12.8 in order for the battery to be charged. The charging voltage must be higher with colder battery temperatures, because lower battery temperature = increased battery internal resistance. So, line voltage in an actual automobile with the engine running should (and usually will) be between 13.3 and 14.5, depending on system parameters and ambient temperature. GM has traditionally installed voltage regulators with higher-than-appropriate setpoints, and the setpoint has been creeping upward over the years such that some of their vehicles now have engine-running line voltage at or near 15v! This has caused there to be widespread problems with GM vehicles losing brake and tail lamp bulbs so often it was considered a safety hazard by the federal authorities, and GM was forced to fix the problem. Rather than correct the improper voltage, they went through the monkey-motion of speccing and building bulbs rated at 14.0v rather than 12.8v. Talk about solving exhaust smoke by shoving a cork up the tailpipe! Typical GM "engineering".
You're simply not looking, then. See above.
A working ammeter tells you what's happening with your electrical system on a real-time, dynamic, right-now basis. A voltmeter doesn't, it just tells you the general trend. An ammeter makes it easier to spot a problem early. I don't say that a voltmeter is useless; it provides a different kind of information. But if I have to pick one or the other, my choice is the ammeter.
Not quite. When the ammeter shows "discharge", that indicates more power is coming out of the battery than is being put in. When the ammeter shows "charge", that indicates more power is going into the battery than is being taken out.

Either an ammeter or a voltmeter can tell you several different things about what is going on with your electrical system, if the gauge is of decent quality and proper calibration and you know how to read it.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

thank you slantsix dan- you were right and i stand corrected. i checked the fine print in my factory electrical manuals for a 76 a body and a 77 f body and the gauge i thought was a voltmeter is in fact an ammeter. guess what misled me was older vehicles gauges were stamped either amps or volts. the round a body duster and valiant gauges from the 70s have a plus or minus 40 on either end and are not identified as to ammeter or voltmeter, but clearly the plus 40 would be amperage output and not volts. one last question , if the ammeter at idle showed the needle slightly to the left, that is toward the minus 40 side, but voltmeter probes across the battery terminals showed a solid 13-14 volts, would that indicate a good battery holding a charge and a good alternator output but an excessive current draw somewhere in the electrical system? thanks