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Thread: Ammeter vs Voltmeter

  1. #1
    Hakosuka sakijo's Avatar
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    Default Ammeter vs Voltmeter

    I'm going to get rid of the clock and put in a Ammeter or voltmeter. I've heard convincing arguements for both at the expense of the other. My question is: Which one gives a better indication of the charging system? I only have the real estate for one.
    Miles

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    Former frequent poster sblake01's Avatar
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    I've always been partial to the voltmeter. All they do is read voltage rather than carry charging current like and ammeter, so they don't run hot. Plus they read constantly (if they are wired un-switched) rather than only when the key is on or the engine is running.
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    philo "Z" opher Zedrally's Avatar
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    What model zed are you talking? I've actually replaced the non functioning clock with a voltmeter in the 240, that way I can monitor charging and battery condition.

    MOM
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    Hakosuka sakijo's Avatar
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    Quote Originally Posted by Zedrally
    What model zed are you talking? I've actually replaced the non functioning clock with a voltmeter in the 240, that way I can monitor charging and battery condition.

    MOM
    I've got the Skyline in the avatar, no Z. I'm looking for the pros and cons of one over the other. I think a standard VDO 2 5/8 inch will go in, though I haven't taken measurements yet.
    Miles

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    2002 Lexus GS 300

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    1978 280Z (stock) TomoHawk's Avatar
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    IMO, the ammmeter gives an indication of what's going ON with the charging circuit, so you'll know if the alternator is doing its job. If the ammmeter is always on the neg. side, you know you're either drawing too much, or the alternator isn't putting out enough, and your battery is going down. Then your engine will eventually quit.

    The voltmeter gives you an indication of how 'full' the battery is. Is the voltage isn't high enough, the engine will quit, or the starter won't turn the engine over.

    You'll notice that it's the older cars, trucks, tractors, etc., that have the ammeters,because ammeters were used when they only had generators on the engines instead of alternators. Even the generators weren't that reliable/efficient, so you needed to know if it had enough RPMs to put out the voltage to charge the battery.

    Contemporary alternators are relatively much more reliable, so battery voltage became more important, though not necessary, so they even got rid of that! Instead we now use the indicator lights.

    Again, it's a metter of preference.

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    RED71Z onuthin's Avatar
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    [QUOTE=TomoHawk]IMO, the ammmeter gives an indication of what's going ON with the charging circuit, so you'll know if the alternator is doing its job. If the ammmeter is always on the neg. side, you know you're either drawing too much, or the alternator isn't putting out enough, and your battery is going down. Then your engine will eventually quit.
    I agree with you,but how do you get your ammeter from jumping back and forth when you add any load to tour system?
    Papa bear,Mama bear,Z bear

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    Semi-retired admin Arne's Avatar
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    Quote Originally Posted by onuthin
    I agree with you,but how do you get your ammeter from jumping back and forth when you add any load to tour system?
    You don't. The ammeter shows the aggregate of the output of your alternator minus the load from the electrical devices. It's going to change when the load changes.

    Ideally, I'd like my cars to have both. But I'll make do with whichever one it came with, it's not worth it to me to add other gauges.
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    RED71Z onuthin's Avatar
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    Quote Originally Posted by Arne
    You don't. The ammeter shows the aggregate of the output of your alternator minus the load from the electrical devices. It's going to change when the load changes.

    Ideally, I'd like my cars to have both. But I'll make do with whichever one it came with, it's not worth it to me to add other gauges.
    My ammeter has been jumping a lot more than normal lately and I have read every thread back as far back as I can remember on ammeters,voltmeters,regulators,and troubleshooting.I had my mind set on the problem being in the meter or the regulator. After reading Arne's reply I went went back out and found the problem was a short to ground in the tailight wires.All the experts said that was the probable cause to start with. That goes to show what happens when you get tunnel vision working out a problem.
    Papa bear,Mama bear,Z bear

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