Generator question again

ok some of you said that this looked like a 12V generator, some didnt think so... the alternator & starter shop i took it too said they didnt know what it was, SO my question is.... HOW do i tell what it is? it dont work so i cant test it. thanks again

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Could be either, it has the shell of a later Delco 12v but who could tell even with numbers it could have been rebuilt either way.
One brush inside is grounded direct to the end frame.
One brush is hooked to the Arm post.
Internally that same brush is attached to the field windings. The F terminal is attached to the other end of the field windings.
If you insulate the Grounded brush with a piece of plastic (from touching the commutaor bars, there should be infinity between all the terminals and ground. With the brush touching, there should be nearly Zero ohms between the Arm terminal and ground, and maybe 2 to 4 ohms between the F terminal and ground. The attached content should solve the issue! Jim
John T system analysis good stuff

(quoted from post at 23:27:40 10/18/11) ok some of you said that this looked like a 12V generator, some didnt think so... the alternator &amp; starter shop i took it too said they didnt know what it was, SO my question is.... HOW do i tell what it is? it dont work so i cant test it. thanks again

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ot much of a generator shop then. Measure the field coil resistance. Most likely an "A-ckt" type gen, so measure Field terminal to Armature terminal. (It it were a "B-ckt" then you would measure Field terminal to Ground(case).
If field resistance is about 1.5 to 3.5 ohms, then probably a 6v unit and if double those numbers, then very likely a 12v unit.

It is in fact a generator now as to it being 6 or 12 volts that is hard to say with out being able to find numbers on it some place unless it does in fact work then it is a matter of checking the voltage it puts out. That said a GOOD shop could tell you what voltage it is so sounds like the shop you took it to does not know generators

Im not smart enough to tell just by looking, but heres a few tidbits that may or may not help.

A genny dont necesarily know its output voltage, its increased if you turn it faster or pump more current through its field coils

Some old Delco gennys that had a black tag were 6 volt while 12 volt had a red tag

Seems like a lot of 6 volts Ive seen had closer commutator spacing (smaller segments) then the 12 volt units

The open unloaded output voltage dont tell you all that much as it will be considerably higher then if coupled up to a load like a big electron bank such as a battery.

If theres a way to answer your question by using an ohm meter, I like JMOR's approach since the field current is one of the most relevant parameteres and their resistance corresponds to the gennys voltage. The fields typicaly may pass say 1 to 4 amps and if a body had the Delco specs he could determine if they are for a 6 or 12 volt gennys butttttttt if he had all the specs he would likely already know what genny it was!!!!!!! I have some specs and maybe knowing the field resistance (As JMOR posted) could answer your question??????

If theres an old fashion mom n pop genny alternator starter shop near you Im sure they can tell either by resistance checks or better yet hook it to a load n spin it

If you posted the tractor make n model number on the appropriate (Ford, IHC, JD etc) forum they can likely tell you what it had originally!!!

John T

i'd attack the question a different way- what machine is it bolted to? what voltage did said machine use originally? is there evidence of it being changed in the past? also look at the rest of the electrical system. how about the battery cables- is it pos or neg ground? i've heard of both 6V and 12V with pos ground, but never heard of 6V with neg ground. is there an ammeter? which way is it wired? if a voltmeter, how many volts to put it in the green? does the starter work? try putting 6V to it and 12V- does 6V seem too sluggish or 12V seem too fast? what seems "just right?"

Doesn't answer your question, but I believe I'd just take it apart and fix it; they're actually pretty simple and often what's wrong with it will immediately become evident when you look at it.