8n altenator problem

hoping someone with more experience can help my grandfather has a 52? 8n side mount dist that had been converted to 12v the battery went dead due to the gm12v alt going kaput i went to a shpo and had it rebuilt and tested while it was off i decided to replace all the wireing from the hackjob that had been done put everything back together and everything is working fine except it doesnt self excite i havnt installed a lamp on it yet so have to rev engine for it to kick in but when it does its only showing putting out 10v on the volt guage and barly moving the amp guage and yes for some reason both are on his tractor any advise ?

(quoted from post at 04:30:08 09/28/12) hoping someone with more experience can help my grandfather has a 52? 8n side mount dist that had been converted to 12v the battery went dead due to the gm12v alt going kaput i went to a shpo and had it rebuilt and tested while it was off i decided to replace all the wireing from the hackjob that had been done put everything back together and everything is working fine except it doesnt self excite i havnt installed a lamp on it yet so have to rev engine for it to kick in but when it does its only showing putting out 10v on the volt guage and barly moving the amp guage and yes for some reason both are on his tractor any advise ?

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Forget the dash gauge for now use a meter you trust and recheck your voltage....Yer 10V does not calculate.... you need to start out with a fully charge battery @12.6V.... yer dash gauge should read 12.6V if it does not you have a bad dash gauge are a serious voltage drop.... Trash the amp meter it has no practical use for daily operation on a 12V system .......

I think Hobo's got you on the right track here.
Since the alternator tested good I'd use a known good meter and
double check the new wiring.

DO verify that you have correct voltage output using a common VOM.

DO disreguard the advice about an ammeter being useless on a 12v conversion.

A dash volt meter may show 12ish volts for a LONG time after your alternator has died, while the low 3a draw of the points is running off the battery. By the time that draw makes the voltage start to sag under 12v and be visible on the commonly availbe 12v dash meters that usually read 8v, 12v and 18v and let you guess at everything in between.. by the time you are dipping enough to nitice ona shakey trractor.. you have a severly discharge 12v battery that liekly won't restart your tractor if you shut her down. a 12v LA battery has a nominal voltage of 12.6v.. at 11.7v it is at 10% capacity.. IE.. severly discharged. I've added a link for a pdf to explain battery voltage vs discharge state. Volt meters are virtally useless without an idiot lamp or ammeter to back them up and actually tell you something abdout which way current is going.

a center 0 ammeter, at a glance, tells you if the battery is charging or discharging based on what quad the needle is in.

charge rate vs time of operation also tells you about the battery.

it's normal too see a initial high charge after starting that tapers off soon as the genny or alt makes up current used to start a machine. if you see a continous high charge rate.. you know there is an issue. for instance.. a shorted cell... you will see excessive charge rate.... a volt meter maght just show 12-14v and you'd think it's fine.. shut down, and poof.. you have a dead battery.... ammeter tells you that.. voltmeter don't

if I had a voltmeter only.. I'd have to have a discharge indicator lamp... atr very least. OR BOTH.. but if only 1, an ammeter tells you more about the condition of the electrical system. volt meter tells you one thing only.
lead acid battery charge state.. vs voltage

have rechecked the wireing the volt meter is whats
telling me 10v the alt tested output at 60a and 13.6
at parts store

yer link reads


Abattery voltmeter is the most
basic system instrument.
Battery voltmeters are
inexpensive, easy to install, and can
provide a wealth of system information
to renewable energy users, RVers, or
anyone who depends on a battery.

12V users don't have to stare at they amp gauge all day a quick glance at start up and a voltmeter will read system voltage :wink: :wink: if it fails it will run the rest of the day on a good bat... IT IS 2012 NOT 1939....

(quoted from post at 21:34:10 09/27/12) have rechecked the wireing the volt meter is whats
telling me 10v the alt tested output at 60a and 13.6
at parts store

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Amos mc, everyone was trying to say you should use a different voltmeter for testing.
The one in the dash may be bad, leading you to wrong conclusions.
Harbor Freight, Walmart, local hardware store.
Any cheap analog multi-meter will work.
Digital ones are a little picky about noise, but would probably work with an alternator.

i replaced both with brand new today am gonna
tripple check connections and wireing in the am at
the rate im going with it and as hot around the
collar as its makeing me i have my eye on a 460 ford
motor might just tear it down and add some more
ummpfff

(quoted from post at 23:01:37 09/27/12) i replaced both with brand new today am gonna
tripple check connections and wireing in the am at
the rate im going with it and as hot around the
collar as its makeing me i have my eye on a 460 ford
motor might just tear it down and add some more
ummpfff

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LOL Years ago I had an old Oldsmobile that gave me fits. 455 4bbl.
It ran great, but it would just die out of the blue, "for no reason at all".
Sometimes at idle, sometimes when I was standing on the gas.
I jacked up the radiator cap and drove a new car under it.
Never had another problem with it.
It was a bit pricey, but it fixed it! :lol:

I had the same problem. Thought my alternator had died. Took it off, completely rebuilt it, re-intalled it, still nothing on the voltmeter. Though tI had screwed up the re-build. Pulled it off, went completely through the alternator again, re-intstalled it, still nothing. Now I'm pulling my hair out and using words my wife wishes I wouldn't. Got the bright idea to test the voltmeter. You guessed it, it was dead. So now I have a re-built alternator and a new voltmeter and everything works as it should. Life is good once aagain!!!!!