140 Ammeter

WAYNE A JOHNSON · Apr 11, 2011

if I change from 6 volt to 12 volt, do i need to change the Ammeter too?

Jim350 · Apr 11, 2011

NO. If you change from + to - ground you will probably find the ammeter reading backwards. Just switch the wire on it around.

John T · Apr 11, 2011

I"m with Jim, no need to change the ammeter (maybe have to swap leads if you change polarity). It"s a series current sensing device and dont know or care if a 6 or 12 volt battery has current flowing into or out of it via the meter.

John T

WAYNE A JOHNSON · Apr 11, 2011

Thanks Jim.

Anonymous-0 · Apr 11, 2011

If you use an alternator, it will peg the old 6 volt ammeter. It's true current is current whether 6 or 12 volt, but an alternator can put out 40 amps plus. Your old 6 volt generator only put out maybe 10-12 amps at the most. The old standard ammeter on a 6 volt Farmall was probably a 15 or 20 amp.
Short story. If you install an alternator, you may want to install 60 amp ammeter. Or, you could install a voltmeter. A voltmeter provides more information than an ammeter.
K-Mo

joe33 · Apr 12, 2011

Your last statement is going to make Dick L. spit his morning coffee all over himself.

mkirsch · Apr 12, 2011

Hmm, I don't get where you think a voltmeter shows more information than an ammeter.

With a voltmeter, anything off the peg is displayed as a "positive." Meaning >0 is good, which is not true.

You need to know which voltage indicates what. You need to know that 14.7 is full charge output, and 12.5 is "break even." Anything below that is an indication of a problem.

With an ammeter, you don't even need to think.

If the needle is to the right, it's charging. The farther to the right, the more it's charging.

If the needle is to the left, it's draining the battery. The farther to the left, the bigger the problem.

Anonymous-0 · Apr 12, 2011

I suspected it would raise an eyebrow or two.
Let me add this-- It takes a thorough understanding of the overall charging system to get information other than charge current from an ammeter.
A voltmeter provides more direct information without needing to know how the system operates.
1. Turn on the ignition, the voltage gives an indication of battery state of charge. 12.6-100%, 12.4-80%. About 10%/tenth of volt.
2. While cranking it indicates the quality of the battery. Draws below 9 volts indicates battery may be weak.
3. While running it indicates battery charging. 13-15 volts indicates charging system is working.
Of course it depends on the type and resolution of he voltmeter.

Did that help or did I dig myself in deeper?
K-Mo

140 Ammeter

WAYNE A JOHNSON

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