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Discussion Starter #1
1966 V8 (302ci with MSD ignition and coil - AGM battery, stock alternator)

Just noticed that my ammeter needle never moves. I can switch on the AC and the headlights, and it still doesn't move, whether I'm idling or at speed.

Shouldn't that needle deflect at least when I engage something electrical?

Thanks.
 

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Its a shunt type ammeter design. It is intended to shunt a very small amperage around one of the main power wires and through the meter. A slight imbalance in the resistance at the wire splices, or more likely at the firewall plugs can throw it off. I bought my car new, and I don't ever remember it working. The Rocktman runs a gauge shop that can convert it to a voltmeter if you like, and no one could tell its been changed. Newer cars all use voltmeters. Purists will argue that only an ammeter will give you the information you need. Eh.
 

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I switched over to a voltmeter when I found my ammeter looking like this. . . . .
763069

I find the voltmeter far more useful than the original.
 

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Discussion Starter #4
Its a shunt type ammeter design. It is intended to shunt a very small amperage around one of the main power wires and through the meter. A slight imbalance in the resistance at the wire splices, or more likely at the firewall plugs can throw it off. I bought my car new, and I don't ever remember it working. The Rocktman runs a gauge shop that can convert it to a voltmeter if you like, and no one could tell its been changed. Newer cars all use voltmeters. Purists will argue that only an ammeter will give you the information you need. Eh.
That's got to be it.
So, should be able to run a dedicated wire for it, right? ...but how and from where?
 

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That's got to be it.
So, should be able to run a dedicated wire for it, right? ...but how and from where?
Nope, not without some very specialized equipment to measure resistance very accurately, and then you have to calculate how much resistance in each path equals how much current is flowing. Ford did it but they aren't sharing their design parameters. I don't know of anyone having done that successfully. You might try cleaning the contacts in the firewall plug, and see if that helps, also check the ammeter to make sure no smoke has leaked out (all electronics runs on smoke and when it leaks out it doesn't work ;), otherwise go with a voltmeter conversion.
 

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Discussion Starter #7
Why so precise? After all, the gauge is not degreed, and all I want to see is a positive or negative deflection, right?
When I buy an ammeter on line, I do not recall any need to meet certain specifications.
...again, e-ignorant, just asking 4th grader questions...unless one proves to be Einsteinian..
 

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Why so precise? After all, the gauge is not degreed, and all I want to see is a positive or negative deflection, right?
When I buy an ammeter on line, I do not recall any need to meet certain specifications.
...again, e-ignorant, just asking 4th grader questions...unless one proves to be Einsteinian..
You would have to backward engineer what they did to make it work, and have the equipment to do it, but be my guest- many discoveries have been just dumb luck or happenstance ;).
 

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Discussion Starter #9
More resistance = greater deflection? ...or vice versa?
I'm thinking I could plumb a potentiometer in the line and vary the resistance until I get a response.
...if only I knew what I was talking about
 

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More resistance = greater deflection? ...or vice versa?
I'm thinking I could plumb a potentiometer in the line and vary the resistance until I get a response.
...if only I knew what I was talking about
There are two wires connected in parallel, with the meter in series with one of them. There are probably milliohms difference between the two, and the ammeter uses this slight difference to get an approximation of the current flowing in the main wire. It was a lousy system that didn't work well or for long usually. It was just too easy to get unwanted resistance where you didn't want it. If you've got a working ammeter you are definitely in the minority. The wire harness, connectors and meter all have to work perfectly. Hence the later use of the voltmeter in modern cars.
 

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Hi , there maybe some interesting info this thread.

It helped me with my working ammeter.

cheers
Rob
 

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Welcome to the club. I'd bet that at least 75% of them don't move enough to even see it. Cleaning the connections is supposed to help.
Been there, done that. I've seen them go from dead to full travel with cleaning of the harness connectors.
 

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Discussion Starter #13
Hi , there maybe some interesting info this thread.

It helped me with my working ammeter.

cheers
Rob
Rob - FANTASTIC! Thank you! THat article is incredible. Fellow spent the hours and hours figuring it out, and then writing it all down for others to use.
Thanks again.
 

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No problem.
Wish I could remember information on ocular disorders as well as I remember mustang stuff.:LOL:

Rob
 

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No problem.
Wish I could remember information on ocular disorders as well as I remember mustang stuff.:LOL:

Rob
I'm a huge fan of Dr. Karl Citek's research on horizontal gaze nystagmus.

My 1966 Mustang ammeter never moved that I could see since owning it in 1992. It looked a little burned on the back at the copper winding so I bought an NOS one at the Nashville show in 2004. It never moved that I could see, and my early searches on the web showed it probably never would. Then one day last month I was following my son as we left a gas station in both our 66s, and suddenly I see this little flicker of the needle to the right. Cool moment, but I'm thinking of having all 3 of our 66s converted to voltmeter guts by Rocketman.

Edit: just started my car to go for breakfast and from OFF to running at 1200 rpm it moved about the thickness of a hair toward Charge haha .
 
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Welcome to the most USELESS guage in the entire 1965-1966 5-Dial Cluster... When it is working, It barely moves to the right... The D C stands for DISCHARGE and CHARGE....

I decided to make mine more useful and took a different route...

763161
763162
763163
 

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Discussion Starter #18
With all the gauge conversion stuff being done to many older cars, I'm wondering what it would take to put a "modern" ammeter into the dash panel, using the original ammeter dial face?
"Modern" meaning one you get off the shelf in an auto parts store and which you easily just wire it in, and bam, it works and works forever.
I've seen many gauge conversions, including clocks, oil pressure, temp, etc., using more modern gauges while retaining the original old-timer gauge faces.
Surely one of youse smart guys can figure out a similar conversion, nyet?
 

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I decided to make mine more useful and took a different route...
Tony, it looks like two different gauges there. The bottom one looks like a Rocketman gauge. Is the upper one a conversion? What routes did you take?
Thanks.
 
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