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Amp Gauge 'Adjustable'?

Discussion in '"Stock" Alpine' started by Mike Armstrong, Sep 26, 2016.

  1. Mike Armstrong

    Mike Armstrong Bronze Level Sponsor

    Just a nitpick but with all my other gauges reading correctly the Amp gauge kinda sticks out as being off a bit. Whether the key is off or engine running and battery fully charged the Amp gauge never zeros out but instead the needle always settles in just left of the center mark.

    Is there a way to adjust the needle to line up on the center mark?
  2. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    Every 35 amp Alpine ammeter I have seen has the needle slightly off center at rest. It seems like the normal setup. I bent the needle slightly when I refurbished my ammeter to have it sit on center at rest.

  3. RootesRacer

    RootesRacer Platinum Level Sponsor

    Many of these gauges have some adjustment meter mounting screws to allow you to twist the movement to zero them. Otherwise yeah, just tweak the needle for zero.
  4. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    I didn't see an adjustment option, but I might have missed it. Here's a photo of the innards. My recollection is the 4 tabs going into the housing fix the mechanism in place.


    Attached Files:

  5. Mike Armstrong

    Mike Armstrong Bronze Level Sponsor

    Thanks guys, Ill get it taken apart and take a look.
  6. Jay Laifman

    Jay Laifman Gold Level Sponsor

    Interesting. I have the factory ammeter, and it runs just south of 0. But I'm running it with an alternator. I was once told that the more correct/useful gauge for an alternator is a voltmeter - and that an ammeter would run just south of 0 with an alternator. My ammeter on my Tiger, with a generator, works correctly.

    I don't know if there is any truth to this as a possible cause. I only have my observations in my study of two - and I am confident of the advice about a voltmeter for an alternator.
  7. Mike Armstrong

    Mike Armstrong Bronze Level Sponsor

    Huh, didn't really think of that Jay, the Amp gauge being meant for use with the original old Generator, not a more modern Alternator.

    I don't know enough about electronics to know what an affect an alternating current would have on an amp gauge meant for direct current. Maybe a slightly off reading should be expected,?
  8. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    The ammeter reflects the current flowing into the battery or out of the battery. The needle moves based on the electromagnetic field generated by the current flow. It works fine with an alternator.

  9. Jay Laifman

    Jay Laifman Gold Level Sponsor

    As I said, I don't know. I do know the voltmeter is a better gauge for monitoring the health of the alternator/battery.

    But I did think of something else. If the ammeter should work the same for an alternator and a generator, then why does the gauge come to rest at 0 when the car is off? And then go below zero after the initial increase after start up and battery charge? That is, when my car is off, the ammeter is right at zero. I start the car and the ammeter pops up for a little while to recharge the battery from the drain from starting. Then it settles down to just below 0 - lower than it is when the ignition is turned off.

    How about yours Mike A.?
    Last edited: Sep 27, 2016
  10. Mike Armstrong

    Mike Armstrong Bronze Level Sponsor

    Same with mine Jay (though, it never settles at zero), it's at +50 after startup (60amp alternator) then settles down close to zero (where it was before start) after a few minutes.
  11. Tom H

    Tom H Platinum Level Sponsor

    Guys, the ammeter is very simple. As Mike Hartmann noted (assuming the ammeter is wired in correctly) simply shows the current flowing into or out of the battery, except it does not show current going into the starter.

    With the key off, ALMOST no current is going to or from the battery. But note that there is possible current even when the key is OFF. Anything connected to terminals 1 or 2 on the fuse box are NOT wired thru the ignition switch. That means the headlights and taillights, and Map light as well as likely the clock, radio, or other accessories could be drawing current even with the key off. I believe the negative reading that Mike sees when all is off is simply a mechanical offset in the pointer. He can easily verify that by disconnecting the battery and confirming that it still read slightly neg. But if there is a difference between battery disconnected and key off then he can be sure that there is some small current actually flowing out of the battery even when the key is OFF-. Clock? Radio? Some keep alive circuit in the radio? Alarm?

    Either an ammeter or a voltmeter can be used to monitor the battery and charging system. I see no difference in capabilities that makes one better suited for Alternator vs Generator. For some people, the ammeter is better: simpler to interpret - if the gauge is reading Plus you are charging and if reading Neg you are discharging the battery. But the biggest point against an ammeter is that if it fails into an open circuit you lose all power. For some people the voltmeter is better because it is in parallel with the battery and if it fails open it simply stops telling you about the system but does not disable the power. But the interpretation of the state of your charging system is a bit trickier with a voltmeter as you need to understand what level of voltage it SHOULD show under various charge conditions.

  12. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    An easy way to add a voltmeter is to get one that plugs into the cigar lighter. I have an Innova Equus 3721. It has a digital read out and colored lights to indicate the status. It works well. There are also models with usb ports, or you could get a Y-cable if you need to power some other item as well.


    Attached Files:

  13. Mike Armstrong

    Mike Armstrong Bronze Level Sponsor

  14. Tom H

    Tom H Platinum Level Sponsor

    Looks great , Mike. And I can see from the before pic that it would be just a bit annoying!

  15. RootesRacer

    RootesRacer Platinum Level Sponsor

    Ammeters like these usually end up showing a charge current offset as the result of a huge current spike that causes the needle to hit its stops which bends the needle. Bending it back should make the meter good as new more or less.
  16. Jay Laifman

    Jay Laifman Gold Level Sponsor

    My father who did once tell me that the voltmeter was more appropriate for the alternator (who was an electrical engineer and rocket scientist), is not around anymore to ask for clarification! I could be forgetting this part, but I have a vague memory that it might have been, perhaps marginally, that a voltmeter might give a warning of things going south on an alternator system whereas an ammeter won't show it until it's not working. But, again, not sure on that part.

    If anyone cares, SS does sell a voltmeter that more closely matches the rest of the gauges.
  17. Tom H

    Tom H Platinum Level Sponsor

    Jay, I think you just proved the point I made earlier - that interpreting what the voltmeter tells you is less easily understood than what an ammeter tells you!

  18. RootesRacer

    RootesRacer Platinum Level Sponsor

    Tom, I think you may have swapped opinions on this ;)

    An ammeter tells you that the battery is getting charged or getting discharged.

    A voltmeter tells you that there is voltage for some reason.

    The battery doesnt charge until the alternator/generator develops enough voltage to exceed the batteries potential which varies by state of charge, temperature and phase of the moon.

    Knowing what the battery voltage should read under all conditions to determine if all is well is a bit tougher than looking at the ammeter needle and just knowing it.

    When I start the car I know the ammeter should read high for a while and then settle down near zero. If ever I am driving the car and I see negative charge (discharge) then I would know that there is a problem.

    At what charging voltage would one be concerned of a discharge condition?

    I dont know either...
  19. Paul A

    Paul A Alpine Registry Curator Platinum Level Sponsor

    Interpreting a voltmeter does not require a degree in electrical engineering. When things are charging and the electrical system in your vehicle is performing normally it will be reflected on the reading shown on the voltmeter. For most of us it will be a reading around 13.5 or 13.6 volts after startup. The following is from GM:

    "Cold, the alternator puts out 14.7 volts and because of the 0.3 volts drop across the ignition switch contacts, the dash voltmeter will read 14.3 volts. As the alternator gets warm its output drops 1 volt to 13.7 volts and the dash will read 13.3."

    As long as your voltage reading is around 13v or higher your alternator/generator is charging and your system is functioning as it should. If while the engine is running the voltage drops below approximately 12.5v the charging system should be checked.

    And all this in a safer environment as the current to the voltmeter is minimal in comparison to an ammeter.
  20. Jay Laifman

    Jay Laifman Gold Level Sponsor

    Not to mention that the stock ammeter has a warning label right across it! It says "LUCAS." :)

    Ha! That said, I know full well that many of the ills attributed to Lucas were actually the choice/fault of the car companies who would choose the less expensive stuff to save money. Further, I have actually never had a wiring problem with my Alpine that I didn't cause! That is, in high school, I added a bunch of gauges, a radio, a clock, and driving lights. MY wiring was less that stellar and had issues. I removed all of that around 1988 and never had an issue again.
    Last edited: Sep 29, 2016

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