Ammeter Guage

holgo123

Petty Officer 3rd Class
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Jun 12, 2006
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I have a 1993 Chris Craft Concept 217 BR with a 5.0 L OMC Cobra EFI MPI. I replaced all the original guages with some Faria guages I got on E-Bay. The set of Faria guages had a Voltmeter Guage and the Original guages had a Ammeter Guage. I installed the voltmeter guage where the ammeter guage use to be... I moved the ammeter guage to the side panel where I mounted the depthfinder/water temp guage... Unfortunately it was a while back when I did this and I had the boat sit a while in my garage while I completed a lengthy transom repair... I know some have siad you don't need the ammeter guage, but I already have mounted it and am trying to figure out what wires originally went to the Chris Craft guage. I think I have found the right set of wires, but was wondering if anyone may have an idea of what color wires went to this guage... The wires I think were connected are a yellow with red stripe and purple... There is also a blue (for the light in the guage) and ground... Is there a way of testing it with a multimeter before connecting it? The yellow with red stripe is a fairly heavy guage wire, but the purple isn't that heavy of a guage... Any ideas?
 

Texasmark

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Dec 20, 2005
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14,544
Re: Ammeter Guage

The ammeter is in series with the output of the alternator/generator, hence it has to be as large a wire as the output (high current)....10 AWG is a good starting point. Butttttt what goes inna comes outta. So the wire size in has to equal the wire size out that goes to the battery to recharge it.

The voltmeter only measures volts and that can be accomplished with 20 AWG more or less. Doesn't really matter the size of either wire since it operates on milliamperes.

The ammeter is plumbed from the alternator output to the battery (in series). The voltmeter is plumbed from the alternator to ground (across the circuit....in parallel).

Does that help?

Mark
 

holgo123

Petty Officer 3rd Class
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Jun 12, 2006
Messages
89
Re: Ammeter Guage

I think I have one leg of the circuit... I will probe around and see if I can find the other leg... I wish I had marked them when I disconnected the original guage...
 

bruceb58

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Mar 5, 2006
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30,454
Re: Ammeter Guage

I would either ditch the ammeter or mount it back in the engine compartment so that the length of wire going to it was short.
 

Silvertip

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Sep 22, 2003
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28,758
Re: Ammeter Guage

I agree with Bruce. A voltmeter is more valuable at the helm and a heck of a lot easier to wire. Put the ammeter at the engine and just check it periodically out of curiosity. Or better yet, mount a clock, hourmeter or compass in the hole and pitch the ammeter.
 

Chris1956

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Mar 25, 2004
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Re: Ammeter Guage

A voltmeter will tell you IF the alternator is charging, but the Ammeter will tell HOW MUCH your alternator is charging. For me, all I need to know is that my alternator is charging. The voltage regulator will take care of the rest. Also, an ammeter can be a fire hazard since they use heavy gauge wire and are not fuzed.

I second the recommendation to ditch the ammeter or mount it in the engine compartment.
 

cbavier

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Apr 8, 2007
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1,363
Re: Ammeter Guage

A voltmeter will tell you IF the alternator is charging, but the Ammeter will tell HOW MUCH your alternator is charging. For me, all I need to know is that my alternator is charging. The voltage regulator will take care of the rest. Also, an ammeter can be a fire hazard since they use heavy gauge wire and are not fuzed.

I second the recommendation to ditch the ammeter or mount it in the engine compartment.

You just answered a question I was about to ask about the difference between the two but I have another question.
I'm not sure which I have. Amp Meter I think because it has the scale but what might cause the Amp gauge needle to quiver when at Idle. As soon as I move the throttle forward a little it settles right down.
 

Silvertip

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Sep 22, 2003
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Re: Ammeter Guage

If the gauge is calibrated 0 - 18 it's a voltmeter and the needle should sit at about the 13 - 14.5 range at anything above idle. If its an amp gauge it will be calibrated -30 0 +30, or -60 0 +60 depending on the alternator output. Minus readings indicate the electrical system is drawing more power from the battery than the alternator is putting back into it. Continuing to run will ultimately leave you dead in the water because the alternator is not working. Plug readings mean the alternator is able to keep up with the load and excess is going into the battery to charge it. In other words, minus readings are bad as the battery alone is providing power. Plus readings are good since the alternator is providing the power and charging the battery. With a voltmeter, anything less than 12.6V reading with the engine running indicates the charging system is not working.
 

cbavier

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Re: Ammeter Guage

Ok Silvertip.
So I have a volt Meter but what would cause the needle to quiver at Idle speed and smooth out as soon as the throttle is advanced? The gauge is working correctly. It never reads minus. It reads about 13 -13.5 volts at Idle. It just quivers until you start to advance the throttle. I've checked the wires and they all seem to be in good condition.
 

Silvertip

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Re: Ammeter Guage

Regulator is probably to blame but as long as its charging I wouldn't be concerned. A voltmeter cannot read negative unless physically connected backwards. Compare voltage to water pressure. You measure water pressure from zero to some number. It cannot be a negative number. An amp gauge measures how much current (not voltage) is present and which direction it is going. If it show POSITIVE it is flowing towards the battery (charging). If it shows NEGATIVE, its flowing out of the battery and the battery is not charging so it will eventually die.
 

cbavier

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Re: Ammeter Guage

Thanks Silvertip:
I wasn't too concerned because it seemed to be working ok, other than the quiver, but everybody who rides with me notices it and asks so since we was on the topic I just thought I would throw it in the mix.
 

wire2

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Jun 25, 2007
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Re: Ammeter Guage

Thanks Silvertip:
I wasn't too concerned because it seemed to be working ok, other than the quiver, but everybody who rides with me notices it and asks so since we was on the topic I just thought I would throw it in the mix.
An automotive (or marine) alternator is really a 3 phase AC generator.
It has a rotor that spins a multi-pole N & S magnet past the stator laminations holding the windings. The output of all 3 windings (phases) is rectified by a bank of 6 diodes.
The current and voltage will pulse from zero to peak and back several times a second at idle.
Your gauge seems to be sensitive to the pulses, but it's nothing to be concerned about. The battery evens it out very effectively.
 

Boatist

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Apr 22, 2002
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4,552
Re: Ammeter Guage

Agree with Wire2
The alternator go from zero to a voltage above your battery voltage. When the voltage get above the voltage of the battery the battery will charge and the meter will move higher. Then it drops back to zero until the next winding does the same thing. So the meter will flucatate at low RPMs, as the speed increases the meter just can rot react quick enough so it looks steady.
 
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